People that take too much require an exhausting amount of energy to defend against. By the time I'm done protecting myself, they've usually got what they want anyway, it sometimes feels like there's no point
I used to be surrounded by the type who answers "no" with "I don't take «no» as an answer". Eventually I started cutting them off my life, and things became so much better. That included a fiancée, a few "friends", and plenty acquaintances. For family the only serious case died so I didn't need to.
For the ones still in my life I make sure that they never get what they want if they insist past a limit. Asking again to be sure, or if conditions changed, is fine; but if you ask again because you want to tire me down, I'm probably boycotting what you want, and I don't care if I sound petty. Eventually they learned when to back down.