hmmm, i have this problem from time to time too. i won't get mad at people that say things that piss me off or if i'm arguing with someone, i just play it cool. but then later i'll lose in a videogame or something trivial that doesn't matter and go flying off the handle. luckily this doesn't happen much any more. i don't know if it's a symptom of holding things in or if it's just more about misdirected anger tho. hard to say. i wish i could give you some advice on how to handle it, but i don't even really know how to handle it when it happens to me.