Pointless anger

I got angry at her for buying an overpriced Japanese book. And I lost more than that amount from a movie I forgot to attend. Recently I realized that I let myself to be angry, sometimes for an unjustified amount of time, because I simply like the feeling of being angry. It is a subtle and harmful addiction. The anger I feel usually stems from incredibly petty matters. It feeds a sense of righteousness and cultivate self pity, which seems pathetic for a grown man when you dissect the issue.