Thanks so much for your detailed response. I will get those two books from the public library.

I think I already understand my colleague. He hates confrontation. He'll do anything to avoid it. I've experienced it before. He was either getting tired of working with me, or else thought the new guy would be better at the project, or just wanted a change. And I've always treated him incredibly well and with absolute tolerance, so I'm sure he just figured that he could just do whatever he wanted and I would get over it eventually. My SO also says I need to talk to him...but really, I truly believe there's no point. He'll say anything to wiggle out of it, manipulate me, convince me everything is fine so that I go away and let him do whatever he wants--and I'll be the one left with another painful situation to ruminate over for weeks or months.

Yes, the job is salvageable if I want... That's another reason I'm not talking to my colleague more than necessary. I think any dialogue right now will end up in me telling him I despise him and I quit. Better to avoid him and this convo for now...for a long time...maybe forever...

Sometimes I ask my SO for praise, to hear anything good about myself, but my SO doesn't get it. I only get comments like "you're cute" "you're really cute" "I like you a lot" etc. I try to explain that I want something tangible I can hold onto, but the response then is that I need to stop looking for validation from other people. I'm not close enough to anyone else to ask for it, so that's that...

I started writing down all my negative thoughts on sticky notes and putting them up, just to get them out and sort of face them and see that they're finite. I think that has helped... I come up with new ones sometimes, but it's slowed down. I will make the list of pros/cons, as you suggested... Unfortunately, there are so many strong pros for staying with my current job. The only con is that it's too painful and I feel I cannot endure it anymore.