Ohhh... I have friends, plural, that suffer with manic depressive disorder and oh my gosh does the tenor of your post remind me of things I have heard soooo many times. So, I really feel above all else that this is your condition talking, not you. I am curious if you have been getting any kind of treatment at all? Have you been on meds or anything? If so, has it helped at all?
One insidious aspect of the condition you have is that it periodically will try to make you do something you would only ever regret, like it is tonight. The only thing I know to say is that you just need to hold on and get through this moment, because when you get back to your normal baseline self you'll be so relieved that you did.
The other insidious thing about being bipolar is these depressive stages keep coming back with a vengeance, especially if left untreated, and they just tear stuff apart. I am the type of person that when her friends are going through something I want to be there for them, give them hugs and say whatever I can to help them get through it. With my friends that have this same condition, I get so worn down by their depressive episodes. Like I feel like I've said everything I can possibly say to help without repeating myself and yet it never seems to do any permanent good. And it's like, duh, words or support won't fix this condition. Medication can definitely mitigate the troubles, but gosh when one of my friends isn't taking care of herself and is off meds, it gets to be too much.
It gets harder and harder for me to reach out each time she cycles through and it makes me feel so terrible. I see myself pulling away a little bit, a lot out of self-preservation honestly, I am a pretty empathetic person and I just take other peoples emotions on as my own too easily and I get dragged down every time. But then, when I kind of stay distant while they go through hell I feel like I'm the worst friend in the world. I love them every bit as much as ever, I just feel I've run out of things to say, also I just feel eroded. I'm sure you feel your own acquaintances doing this to you sometimes. People seeming to turn against you, or who seem to stop caring. I want to tell you this isn't true, we do still care. Always. And everybody that makes you feel that way is very sorry and will be there again for you another time.
So, please get help if you haven't been. You can't like "overcome" this on your own. If you have been getting that help and this is just one of those episodes that got through, just hang on and get through it. Stay away from depressing reading. If you need somebody to talk to, PM me.