Dr. Aziz explains why boundary-setting feels guilty: you've learned to take responsibility for others' emotions and prevent them from feeling bad. You're not responsible for everyone's feelings, and saying no lets others find their own resources.
Chapters
If you feel guilty saying no or setting other boundaries, you have to watch this short because it's going to change everything for you. The reason that you feel guilty is because you're taking over responsibility for everyone else's feelings. And you feel like the main purpose in life and relationships is to make sure no one ever feels bad, ever. Even if you're speaking what's true to you, even if you're asking for what you really want, even if you don't really want to go take care of somebody. So the key here is to realize, one, you're not responsible for everyone's feelings. Two, you're not the sole source for people. So if someone invites you to something and you say no, it's not like, oh, well, I guess I never will have any other social interaction. No, that person can go talk to somebody else, they can go invite somebody else to the thing. You aren't responsible to meet all of their needs. And this is true even for those close to you, even for your partner, it is healthy to say no, and then to force other people to be resourceful and to find other ways to meet their needs besides just with you.