I have a hard time saying no when the other person wants a yes. This is, I think, a very female trait, though I’m sure males do it too. But a resentful, insincere yes is no good.
Prime example: I am so happy to loan out about 60 percent of my clothes, wary but ultimately OK with 35 percent, and dead set on never letting 5 percent out of my sight. While, in the past, I’d give out anything (and then be secretly angry in a way that I totally brought upon myself) now I can just say, “You know, that is actually really special to me and I don’t feel comfortable lending it out. What about this [similar, less-special thing]?”
Anticipating, caring about and hopefully meeting other people’s needs is a legitimate and wonderful thing to do. But so is recognizing your own limits and setting boundaries. It doesn’t have to be a big, confrontational deal:
Q: Do you want to hang out even though you hate me but I don’t know it?
A: You know, I’d love to but I’m afraid I can’t that night.
Q: Can you volunteer for extremely unappealing task for a cause you don’t particularly care about?
A: I’m so sorry, but my plate is pretty full right now.
An explanation is good, but not always necessary, particularly if what the other person is asking of you is unreasonable. If they press you, just stick to the non-confrontational no. “I wish I could, but I’m afraid I can’t.” They don’t need to know that the reason you can’t is because you’ve made a commitment to not being pressed into things you don’t want because of social pressure.