It WILL be okay. I know that feeling. Happens to me all the time and it SUCKS.
Try to do something nice for yourself--cup of tea, run around like crazy, curl up in a ball under some blankets and just BREATHE--whatever you would ordinarily like and find peaceful. (even if right now it feels stupid, if you can just do it, it might help some).
Try and remember that whatever happens, whether your paper is perfect, or half done, or not done at all--it is not the end of the world! Sometimes when I realize this when I have something due the next day that I can't seem to do, miracles happen and a paper is written. For me the hardest thing is trying to think beyond right now. Sooooo hard!! ! But if I can just convince myself it's not the end of the world, I usually feel better.
I don't know if that's helpful, but I hope it is and that you can feel better!