That's a pretty big thing to ask. Like, 'just do this one little thing for me - transform yourself into whatever I want you to be.' It might not work for you, but I'm ok with a friend asking me just not to hurt myself for one day or one night or over one issue. I can give a promise like that and be able to keep it, because I can always wait that long, at least. My T hasn't even asked me to stop, although she suggested rewarding myself for progress when I don't hurt myself for a while. She said that she knew that she couldn't ask that, but she did put limits on it, and I was ok with the limits since I wasn't going to take it that far anyway.

Maybe you could negotiate for something that isn't too big of a step for you, that you can both feel better about. Something that would keep you safer, but not require you to promise more than you are ready to give.