@phoenixhaber, you're in a very dark place, no doubt about it, and it sounds like you've been there a long time. I've been in that dark place and I feel for you. Let me just assure you that dark times do give way, eventually, to light. If you need a rational basis for that claim, think of it as regression toward the mean: extremes, good or bad, move toward the non-extreme. Things will get better.

In the meantime, your task is to separate from the darkness and let it be on the outside, not the inside. It's bad enough when it's on the outside: that is, in the world around you or even in your own body. When it's on the inside—not just the body but the mind—then it destroys. Push the darkness out of the mind and into the outside world. That's pretty abstract advice but it's the best I know, and if it makes sense to you, I hope it helps.