I'm starting to learn to just accept the rejection that I became ultra-paranoid about occurring. I think, "Well, I've already been rejected, so I'll just act like I haven't been." And usually the person I thought this was the case with will keep interacting with me.
And also what I'm learning is that people usually won't tell you even if they are put off by something you did or said. The way I see it, I'll just keep doing whatever I'm doing and if they cut off contact, then fine, because why would I want to continue with the torture of that ambiguity, feeling like they're pushing me away but then suddenly pulling me back in again at random? And if they finally punch me in the face and call me out on something, then good - finally! I'd have something clear to learn and we'd all be on the same page when I apologize. And if they don't accept an apology, they're too stupid to be of further use, and if they do accept an apology and we're good, then that would be a sign of a good friend worth continuing to put energy into.
And also what has helped me is to have to deal with actual rejection. You might have rejection paranoia, but once you have real life, clear cut, in your face rejection, you have to accept that because if you can't learn to let that real stuff go as soon as possible, you'll just keep trudging down and down and down. I think of it like the bludgers in Harry Potter. When someone doesn't answer my e-mail, I'm thinking, "Woah! That one almost hit me and I would have been a gonner, but it didn't. Now I gotta face forward again and focus and keep going."
You have a choice about how to respond to things, you really do. And it's okay to tell yourself things like "I'm incredibly amazing!" even if you know it's not true. It also can't be true that you're an ugly idiot that everyone in the world hates. Why lie to yourself in that direction when it feels better to lie to yourself in the other direction?