For me I frame it less as a fear of rejection and more of a fear of putting someone in the inconvenient position of having to tell someone to go away.

Tell me to fuck off and get lost to my face, fine. I'm the awkward extra wheel no one asked for in this situation, this is just an expected outcome. Tell me something I don't know, lmao.

But the thought that someone came to a bar to have a good time, only to be stained because some irritating creep (me) showed up out of the crowd and reached out unsolicited, well, that's what's soul crushing to me. The idea that my very presence may actively disrupt their night out makes me feel like an unwelcome prick just for being there.

Of couse, that's just a toxic fantasy I dreamed up in my own head. But so is just about any arbitrary mental barrier that prevents otherwise rational people from doing reasonable things.