You have been given a ton of great advice. No is a complete sentence. For me that was difficult when I first started trying to use it to assert myself when I needed to stop being taken advantage of.
i added "that's not going to work for me. " Don't give a reason because the manipulator/user/ control freak will fix your reason. It's difficult , especially if you're a people pleaser and don't like confrontation. The more you say it , the easier it gets.
That's not going to work for me.
why not?
it's not going to work for me. Over and over till they give up.