When this would happen to me, I found these things to be useful. They may or may not be for you. Breathe as deeply and slowly as you can. Eat something salty, like potato chips. Listen to music or watch TV so your mind doesn't gnaw on itself too much. If you have someone you trust, it helps to have them there, but if you don't really trust them obviously it'll make things worse. I really hope things are better for you, those are miserable.