I used to do that when I was a teenage, and I've sorta mellowed out since I was 18. At the time it always felt justified even if it started out of something inane. Also, it was usually aimless anger, like I didn't know why I was angry. Certainly on many occassions I couldn't remember for the life of me what had upset me so much in the first place.
I never really came up with any decent strategies for dealing with this, although in later years when I was feeling down or a bit pissed off at something I would take the dog for a walk, and take my discman. Sometimes I would just walk, other times I would find a park and sit down and think over things before I headed back. Usually this was in the late afternoon or evening, when it was quiet and I could be alone.