You have a good understanding of the problem, which is a good place to make a beginning. Here's what I think it comes down to: You are a sensitive person very aware of other people's feelings. You hate to do anything that you think will cause others to be disappointed. So you've gone through life doing things you don't really want to do because you think that is what it takes to be able to consider yourself a nice person. Still, at some level, you see that this is not entirely fair to you. Problem is how to overcome this.

Sometimes we just have to force ourselves to do something that goes against our habitual nature. That can be hard. The good news, however, is that it gets easier the more you do it. What seems hard right now will actually make your life easier in the long run.

It might also be helpful to mentally investigate where this people-pleasing tendency came from. Childhood would be a good place to look. As a child, were you very invested emotionally in pleasing adults and/or peers? I'll bet you were. Maybe your parents were that way. Maybe it suited their agenda to make you that way. There is definitely a long history from way back when that explains this tendency you have. That's why it's such a big deal to try and approach life differently.