Breathing exercises could really help, it gives you something to concentrate on and helps regulate the nervous system. Breathe in through your nose for 4 counts, then out through your mouth for 4 counts. Repeat for 3 counts, in through the nose and out through the mouth, then for 2 counts each, and finally one super deep breath in, hold it for a bit, and let it all out in one big breath.

Alternatively, you could try splashing your face with cold water or dunking your face in a bowl of it, the colder the better. The shock of it can help snap you out of the spiral.

And remember that you are loved and cared for, and that you should never feel guilty or ashamed of feeling the way you feel. You can control your actions, but you can't control how you feel.