Thank you for posting this question, Sophia. It makes me think. And the follow-up posts are really good too. Me, I have had so many bad interactions with people, over so long a length of time, it's led me to think about what I guess would be another element to the problem of "other people pain."

I would guess that all of us have internalized, unconscious ideas about what other people are like and what relationships are like. We absorb that from mom before we can talk. If we've had bad experiences with mom as a baby, our basic internal picture or idea of other people can be totally off base or just non-existent. I think that's why I stay away from people, and why I've been rejected so many times, time out of mind.

So maybe it's not JUST fear of pain, but also simply confusion as to what to do. If you were babied right, you've got the map of a relationship, but if not, it's a blank, or a wrong map that only gets you rejection from normal people.
Hope this helps.