I know this is the not the best solution, but here is what I do:
1. I remove myself from the situation if possible. I go away from all people so that I could sort out my racing thoughts. When I feel like I can be trusted not to say anything stupid, I allow myself to rejoin civilization. (this is not always a short process)
2. If I can’t leave the situation, I clam up and don’t say a word. this is how my friends know when I am upset- I just don’t talk- period.
3. I’ve tried this a few times, and it worked for me: if I am really mad at someone, I take my emotions to the opposite extreme and I try to be extra sickly sweet to them. I don’t know why this works, but it does, and its very satisfying, for some unknown reason.