How to train ChatGPT on your coaching voice. The voice-profile method: ten samples in, one style card out, thirty minutes once.
"Write in a friendly, direct voice" gives every coach who types it the same draft. What works is evidence: ten things you actually wrote, a prompt that reads them and writes down what you do (how long, how you open, the phrases you repeat, the words you never use), and a card you paste into every prompt afterwards. This page is that method, with the profile prompt, an example card, the prompt that uses it, three tests that show whether it worked, and the short list of messages that must never come out of it.
By Markus Evers · Published 6 September 2026
the short version
To train ChatGPT on your coaching voice, collect ten samples you wrote (captions, check-in replies, emails, DMs), paste them into the voice-profile prompt, and keep the 150 to 250 word style card it returns. Paste the card at the top of every prompt or into custom instructions, test it, and never let it write the hard messages.
Which writing samples does ChatGPT need to learn your voice?
ChatGPT needs ten samples across four surfaces to copy a coach's voice: three or four Instagram captions, three check-in replies with the client's name removed, two emails, and one or two DMs. Variety matters more than volume, because each surface shows a different length and register, and the model will otherwise fill the gaps with generic fitness writing. Pick things you would happily send again today, and include one where you were blunt. The card is why the answer to "which AI writing tool is best for a coach" is the one you set up; the five-row pick is on the best AI tools page.
| Surface | How many | What it teaches the model | Which ones to pick |
|---|---|---|---|
| Instagram captions | 3 to 4 | Your public voice: hooks, how you teach in public, how you ask. | One client win, one opinion, one practical post. Include the one where you were blunt. |
| Check-in replies | 3 | Your coaching voice: how you acknowledge, instruct and ask, one to one. | An on-track week, a missed week, a good result. Remove the client's name first. |
| Emails | 2 | Your longer form: openers, sign-offs, how you structure three paragraphs. | A welcome or onboarding email and one reply to a question. |
| DMs | 1 to 2 | Your shortest form: how you sound in two lines. | A reply to an enquiry and a reply to a client's quick question. |
Strip the samples before you paste. Your own words are yours to share; the client's are not. Remove names, anything about a client's body or health, and any line a client wrote. A check-in reply with "[name]" in place of the name teaches the model exactly as much about your voice.
What prompt turns your samples into a voice profile?
The profile prompt reads your ten samples and returns a style card of 150 to 250 words containing only what the samples prove: length by surface, openers quoted verbatim, how you address people, six repeated phrases, how you instruct, how you close, rhythm, punctuation, the words you never use, tone in three evidenced words, and one line on what you talk about that other coaches do not. It is told to write "no evidence" rather than guess, which is what stops the card from describing a generic coach.
The voice-profile prompt (ten samples in, one style card out)
When to use it: Once, at the start, and again every few months as your writing changes.
What to paste in: Your ten stripped samples, unedited, in the slots at the bottom.
I am an online fitness coach. Below are ten things I wrote myself, unedited, across captions, check-in replies, emails and DMs. Read all of them, then produce a VOICE STYLE CARD I can paste at the top of prompts or into custom instructions so that drafts read as if I wrote them. The card must be 150 to 250 words, in short bullet points, and contain only what the samples prove: 1. Typical length by surface (caption, check-in reply, email, DM), in sentences and words. 2. How I open, with three of my actual first lines quoted verbatim. 3. How I address people (name, "you", nickname) and how often. 4. Phrases I repeat, at least six, quoted verbatim. 5. How I give an instruction, two examples quoted. 6. How I close and sign off, quoted. 7. Sentence rhythm: what I actually do (short after long, fragments, questions, lists or no lists). 8. Punctuation habits: exclamation marks, dashes, brackets, emoji, capitals. 9. Words and constructions I never use, derived from what is absent (for example: no "journey", no "crush", no lists of three, no rhetorical questions, if that is true). 10. Tone in three plain words, each backed by one quoted example, not compliments. 11. One line on what I talk about that other coaches do not (from the samples only). Do not improve my writing. Do not add advice. Do not invent a phrase I did not use. If a category has no evidence, write "no evidence" rather than guessing. Output the card only. SAMPLE 1 (caption): [PASTE] SAMPLE 2 (caption): [PASTE] SAMPLE 3 (caption): [PASTE] SAMPLE 4 (caption): [PASTE] SAMPLE 5 (check-in reply, name removed): [PASTE] SAMPLE 6 (check-in reply, name removed): [PASTE] SAMPLE 7 (check-in reply, name removed): [PASTE] SAMPLE 8 (email): [PASTE] SAMPLE 9 (email): [PASTE] SAMPLE 10 (DM): [PASTE]
What does a finished voice style card look like?
A finished style card is about 200 words of evidence, not description: every claim in it is a quote or a count from your samples. The example below was written for an illustrative coach to show the shape; yours will have different phrases, a different rhythm and a different "never uses" list, and that difference is the whole point. Save it in a note, and paste it into prompts using the second block.
Example style card (for the shape, not for you)
When to use it: Read it to see what a good card contains. Do not use it: it describes someone else.
What to paste in: Nothing. Your own card comes out of the profile prompt above.
VOICE STYLE CARD (illustrative example, from a coach who is not you)
Length: captions 60 to 110 words; check-in replies 4 to 6 sentences; emails 3 short paragraphs; DMs 1 to 2 lines.
Openers: "Quick one." / "Two things from this week." / "Sara, that squat video."
Address: first name once, then "you". Never "guys", never "team".
Repeated phrases: "the boring version works", "hold the plan", "that is the whole tip", "we fix the total first", "not a report card", "say the word".
Instructions: "Add one set. Nothing else." / "Weigh in Tuesday, same time, send me the number."
Closes: a question, or "Speak Monday." No sign-off name in DMs.
Rhythm: one long sentence then a three-word one. Fragments allowed. Lists only in emails, never in captions.
Punctuation: no exclamation marks, no emoji, full stops between fragments, no dashes.
Never uses: journey, crush, smash, game-changer, "let's go", rhetorical questions in a row, "I hope this finds you well".
Tone: dry ("Fair question. The answer was yes."), specific ("27 of 30 logs"), warm by action not by adjective ("send me the number").
Distinctive: talks about lunches and Saturdays more than workouts. Using the card: the prompt header for every draft
When to use it: Every time you ask for a caption, reply, email or DM.
What to paste in: Your card, then the surface, the topic, one specific detail and the ask.
VOICE STYLE CARD [PASTE YOUR CARD HERE] Write in the voice described by the card above. Copy its length for this surface, its openers, its repeated phrases where they fit naturally, its punctuation habits and its rhythm. Never use anything in its "never uses" list. Do not add a summary sentence or a closing offer. Keep every fact I give you exactly as given and invent nothing. TASK Surface: [caption / check-in reply / email / DM] What it is about: [ONE SENTENCE] The specific detail to include: [e.g. "27 of 30 logs" / "the 6am sessions"] The ask at the end, if any: [ONE ASK or "none"] Output the draft only, labelled "DRAFT FOR COACH REVIEW", then one line listing which phrases from the card you reused.
Where to keep it. Once the tests below pass, put the card in your assistant's custom instructions (in ChatGPT under Settings, then Personalization, or inside a Project) so it is read before every chat and you stop pasting it. Keep the note too: you will want the same card in Claude or Gemini, and instruction fields change. The rest of the standing setup around the card, both instruction boxes and four Projects, is in ChatGPT custom instructions for fitness coaches; in Claude the card goes at the top of the Content project, set up in Claude Projects for fitness coaches.
How do you test whether the voice profile works?
Test the voice profile with three prompts on surfaces you already have real examples of: a caption on a topic you have posted about, an on-track check-in reply, and a two-line DM. Put the draft next to the real one. A pass is something you would send after a small edit with none of your banned words in it. A fail usually means the samples were too similar to each other, not that the card needs more adjectives.
| Test | Pass looks like | Fail looks like |
|---|---|---|
| 1. A caption on a topic you already posted about | You would post it after a small edit; the opener could be yours; none of your banned words appear; it does not end on a moral. | It opens with a question, uses "journey" or a list of three, or reads like any coach. |
| 2. A check-in reply for an on-track week | Four to six sentences, your phrases in it, one adjustment, one ask, in your rhythm. | Praise inflation, "great job!", a paragraph per metric, or "let me know if you have any questions". |
| 3. A two-line DM reply to an enquiry | Two lines. Sounds like your DMs, ends on a question or a next step. | Five lines, a greeting that you never use, an emoji you never use. |
What should you never let ChatGPT write in your voice?
Six messages should never come out of a voice profile, however good it is: the reply to a slipping client, an apology, a testimonial or client quote, an answer to a medical or injury question, anything sent to a named client unedited, and the conversation about money or ending coaching. A profile makes drafts sound like you, and these are the messages where a client is specifically listening for whether it is you.
- 01
The message to a client who is slipping, upset or going quiet. The model gives you bullet points; you write it.
- 02
An apology, for a missed reply, a wrong plan or a billing mistake.
- 03
A testimonial, a client quote, or a client story that puts words in someone's mouth.
- 04
A reply to a medical, pain or injury question. Refer out or answer yourself.
- 05
Anything sent to a named client without you editing it and adding one detail only you know.
- 06
The conversation about payment, a price rise, or ending the coaching.
The card feeds every prompt library on this site, and all of them are in one free download, the AI prompt pack for online coaches. For captions, the twelve rules and eight sub-prompts in Instagram captions that don't sound like AI take the card as their ABOUT ME block. For the weekly reply, ChatGPT prompts for check-in replies use it as the style card header and hand the slipping client back to you. The drafts live wherever you draft; the message the client reads is sent from Coachway, after you have edited it, from the same screen as their check-in and plan.
Frequently asked questions about training ChatGPT on your voice.
How do I train ChatGPT to write in my voice as a fitness coach?
Collect ten pieces you wrote yourself across the surfaces you use (captions, check-in replies, emails, DMs), paste them into the voice-profile prompt, and keep the style card it returns: your sentence length, openers, repeated phrases, sign-offs, and the words you never use. Paste the card at the top of every prompt, or into the model's custom instructions, and test it with three prompts before you trust it. The whole setup takes about 30 minutes once.
Can ChatGPT actually learn my writing style?
It can copy it convincingly from samples, which is different from learning it. Given ten real samples and a style card, a model reproduces your sentence length, rhythm and vocabulary well enough that a draft needs a two-minute edit instead of a rewrite. Without samples it produces the average of every coach on the internet, whatever adjectives you give it. The samples are the training; the card is the memory.
How many writing samples does ChatGPT need to copy my voice?
Ten is enough, if they are varied: three or four captions, three check-in replies, two emails, one or two DMs. Fewer than five and the model fills gaps with generic fitness writing; more than fifteen adds little. Choose samples you would be happy to send again today, not your most polished, and include one where you were blunt.
What is a voice style card?
A style card is a 150 to 250 word description of how you write, derived from your own samples: typical length, how you open, how you address the client, phrases you repeat (quoted verbatim), how you give an instruction, how you close, sentence rhythm, words you never use, and tone in three plain words backed by evidence. It is the thing you paste into prompts or custom instructions so every draft starts from your rhythm.
Should I put my voice profile in ChatGPT custom instructions?
Yes, once you have tested it. Custom instructions (in Settings under Personalization, or in a Project) are read before every chat, so the style card there means you stop pasting it. Keep a copy in a note as well, because instruction fields change and you will want the card in Claude or Gemini too. Update it every few months as your writing shifts.
How do I test whether the voice profile works?
Run three prompts: a caption on a topic you have already posted about, a check-in reply for an on-track week, and a two-line DM reply. Compare each to something you actually wrote. Pass means you would send it after a small edit and it contains none of your banned words. Fail means it reads like every other coach, and the fix is usually more varied samples, not more adjectives.
What should I never let ChatGPT write in my voice?
The message to a client who is slipping or upset, an apology, a testimonial or any client quote, a reply to a medical or injury question, anything that goes to a named client without you editing it, and a hard conversation about payment or ending coaching. A voice profile makes drafts sound like you, which is exactly why those five have to actually be you.
Will clients be able to tell I used AI?
Not from a draft written from your samples and edited by you with one real detail added. They can tell when the reply contains nothing only you would know, arrives faster than usual with a summary at the end, or sounds warmer and more balanced than you do in person. Coaches have lost clients over check-in replies that read as generated. The rewrite with a specific detail is not optional.
Ten things you wrote, one card, three tests. After that, every draft starts from your rhythm instead of the internet's, and the messages that have to be you still are.
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