I'm old but a habitual and lifelong people pleaser.
When I was ...not so old, I saw a response to a situation from another person and chose to adopt it and it has worked really well for me ever since.
It's to answer immediately with something like, "Good God no, I wouldn't consider that!" or "Not a chance!"
It's amazing how it gets people immediately in their place.
My first outing with this was when we bought a caravan to live in while we had a load of work done on the house but my sister, who has spent her entire life getting what she wants, when she wants it, said that she would borrow it for a holiday with her kids before we moved into it.
Sister has a long history of borrowing stuff, breaking it or allowing it to become utterly ruined and handing it back in that state without even having the good grace to explain or, not even giving stuff back at all.
I said the former, above and, for the first time in her life, she actually stopped in her tracks, asked again and I said, "No. I've seen what things look like after you have used them and we have to live in that caravan."
I have been NC with her for nearly 20 years now over stuff far worse than her destroying mine and other peoples property but I was amazed at how well the immediate and affronted response worked on her and I have used it many times since with CF's.