Classic case of depression, actually it sounds like a pretty bad case, but obviously you have a lot of strength so you can get through this, absolutely. Don't believe for a second that their aren't honest people, you have been contemplating this, but it isn't true, and you will find that out eventually, accept it deeply, although there may be none in your life right now. In my experience disillusionment with a girlfriend is about the worst, runner up being getting fired.
If nothing else works, I suggest thinking about moving, pulling up roots and going somewhere else. You're a dancer, how about New York? Or San Francisco? There should be lots of places. I know, you probably don't want to think about something so hard now, and probably you shouldn't but down the line it's a possibility.
I went to a Richie Havens concert in 1973 (I think) and he said something on stage I've never forgotten, he just said it kind of out of the blue: "People think it's easy to give up, but it is not. It's very hard to give up." You haven't given up, far from it. You say the rational part of you says you should give up. Maybe there are some things you should give up on, or rather some attitude adjustments are in order, but giving up on life and yourself isn't an option. I'm big on aphorisms and one of my favorites from William Blake is this: "The soul of sweet delight can never be defiled."