Rehearse a difficult conversation before I have it

I have a conversation coming up that I'm not looking forward to. I want to practise it, not plan it.

Who I'm talking to: [THEIR ROLE AND YOUR RELATIONSHIP]
What it's about: [THE SUBJECT]
What I want out of it: [YOUR ACTUAL GOAL — not the diplomatic version]
What they probably want: [YOUR HONEST GUESS]
What I'm worried they'll say: [THE THING YOU'RE DREADING]

You're going to play them. Rules for you:
- Be realistic, not difficult for the sake of it. Real people are mostly reasonable and occasionally not.
- Don't concede quickly. If I make a weak argument, push on it the way they would.
- Stay in character until I type STOP.
- If I say something that would genuinely land badly, react the way a person would — don't be a good sport about it.

Start with their opening line. Not a summary of their position — the actual first thing they'd say.

When I type STOP, come out of character and tell me:
1. Where I lost them, if I did, and the exact moment
2. The thing I said that I should cut entirely
3. The strongest point I made, so I keep it
4. What I never got to, and whether it mattered
5. One sentence that would have made the whole thing easier, and where it should have gone

Don't reassure me. If I handled it badly, I'd rather find out here.