Working out.
In my experience anger can be the result of too much pent up negative energy. I personally enjoy weight lifting b/c I find the experience very meditative, but any exercise that leaves you worn out works.
Also cut out as much sugar as possible. Sugar messes with the neurons in your head and in my experience my moods are much worse when I've been eating garbage.
Other than that, time and patience and learning to catch yourself when you're feeling overwhelmed.
I was a pokemon tgc gym leader when toys r'us had tgc meetups, I had the original base deck (which was stolen, that hurt!)
Fell out after black & white.