You paste in your own email, ask for a version of it, and what comes back has been to business school. It thanks the customer for reaching out. It is delighted to assist. It says "furthermore" in a message about a broken tap.
So you rewrite it. And once you have rewritten the third one, you stop asking, because doing it yourself was faster.
That is the point most people quietly give up on AI, and it is a fixable problem. The AI is not failing to write well. It is writing in the only voice it has, because nobody has told it yours.
The fix is a file, not a better request
Asking nicely does not work. "Write it in a friendly, professional tone" is the instruction every business on earth would give, so it produces the writing every business on earth gets.
What works is a short document describing how you actually write, which you paste into your AI's settings once. After that every draft starts from your voice instead of from the default one.
It takes about 15 minutes to build, and you build it from writing you have already done rather than from your own description of yourself. That distinction matters more than anything else in this guide. Ask somebody how they write and they answer aspirationally: warm, professional, approachable. Read what they sent last Tuesday and you find short sentences, no greeting, and a habit of starting with "So".
The writing is honest. The description is a wish.
Find your samples first
Before you write anything, go and get 5 things you have written and were happy with. Not your best work, your normal work.
Good places to look: sent emails to customers, quotes with a note attached, an Instagram caption you wrote yourself, a text to a supplier, the last thing you posted in a community group.
2 rules about what to pick. Real customer-facing writing beats anything you wrote for an audience of one, so a quick text to your business partner is less useful than a reply to a customer. And pick things you were pleased with, because you are about to teach the AI to imitate them.
If you can only find 3, start with those.
The prompt that builds the file
Paste your samples in, then paste this. It interviews you rather than asking you to describe yourself, which is the whole trick.
I want to build a short file called "Voice" so that everything you draft for me sounds like me instead of like generic AI writing.
Above are [5] pieces of writing I have done. Read them first and tell me what you notice about how I write: sentence length, how formal I am, words I reach for, words I avoid, how I open and close. Show me your read before you ask me anything.
Then interview me one question at a time to fill the gaps. Cover: words and phrases I would never use, words I always use, how formal I am with customers compared to everyone else, and any formatting rules I care about such as spelling, emojis and paragraph length.
Rules for you: one question at a time, and wait for my answer. Show me a draft and let me correct it rather than asking me to describe my own voice in the abstract, because nobody can do that accurately. Push me hard on the list of words I would never use.
When we are done, write the finished file. Then prove it works: I will give you a real email I need to answer, and you draft the reply using the file. Australian English throughout.
Make this prompt yours
Fill these in and the prompt below becomes yours. Nothing you type leaves this page.
Where to put it once it is written
2 places, and they do different jobs.
Your saved instructions are the right home if you mostly write as yourself. It applies to every conversation automatically, forever, and there is nothing to remember. That is the same box the standing instructions guide covers, and the 2 files sit together happily: one says what your business is, the other says how you sound.
A project is better if you write in more than one voice. A café owner posting as the café and also writing to their accountant needs 2, and projects keep them apart without either leaking into the other.
Where this stops working
It fades in a long conversation. After a long back-and-forth the AI drifts back towards its own register. Your file has not failed. This is a limit of how memory and context work, and starting a fresh chat for anything that matters brings the voice straight back.
It cannot give you a voice you do not have. If your samples are 3 lines long and slightly stiff, the file will faithfully reproduce writing that is 3 lines long and slightly stiff. That is working correctly. The file copies how you write, so if you want to write differently, change the samples rather than the file.
Structured writing resists it more than prose. Quotes, invoices and anything with headings and a table will come out sounding more neutral than an email will, because the format does more of the work than the voice does.
It will not survive you not reading the output. The file gets you a draft that sounds like you, which is a much better starting point than a blank page. It does not get you something to send unread, and a customer will always notice the sentence you did not write.
15 minutes, then it is done forever
Go and find 5 things you have written. Paste them in with the prompt above. Answer the questions honestly rather than flatteringly, and push back hard when it asks which words you would never use, because that list changes the output faster than anything else in the file. Then paste the finished file into your settings.
Test it properly: take a real email sitting in your inbox right now, ask for a reply, and read what comes back. You are listening for one specific reaction, which is quietly thinking "that sounds like me". If you hesitate, tell the AI what was off and have it revise the file. A voice file you do not quite believe in is one you will stop using by Thursday.