That sucks big time. For me I try to breathe in for eight seconds, hold it, then slowly breathe it out. However, if I don't want to do that or it doesn't work, my number one resource is always music. I go to my room or put my iPod in and turn it up as loud as possible. I listen to whatever I'm in the mood for, space out, and just forget everything. It seriously works, even if you're in a crowded place. I also go on the Internet, read a book, or just go for a walk. I have to keep preoccupied though and I have to hear noise, otherwise I can't drown out my thoughts. If you ever feel like you're going to punch the person, just go outside and punch a tree (this can have bad consequences though, trees are very short-tempered) or punch a pillow inside. Bury your head in the pillow and scream if needed. Sometimes it's good to let everything out and not keep it all bottled up.