skating's good, but doesnt help if you let yourself get mad when you skate.
the best thing i do is try to focus on the moment. try not to worry about the future. if something sucks (like youre situation in class), youve gotta think 'ok this sucks, but how does being pissed help?', and use that to calm down.
you can still be pissed off, but dont focus on how pissed off you are.
a lot of it is probably chemical, look at what youve been eating, make sure youre eating fruits and healthy shit.
also if youre spending a lot of time on your own, thatll drive anyone crazy. gotta try to avoid that whenever possible.