Why do guys get sooo pissed off at stupid things?

Im dating this guy and he got really pissed off last night cause he found out I don't have the same feelings as he does for me yet! but he knows still want to date him and he knows I like him...so why did he start being mean to me? and angry at "himself" he says his sorry and that he knows he over reacted... but still why do men get upset over nothing?