It's good that this situation is such an anomaly to your personality. Perhaps it was upsetting enough that you just haven't been able to effectively purge the trauma out of your system.

I'm probably not the person to offer advice on this topic, but maybe it's more about the emotional side of the anger, rather than working out the physical feelings of things?

One thing that I've done in the past that has helped me deal with being really mad, is to write a letter that will never get sent. It's not about the other person, it's about getting it out of my system. You can write a really vulgar, explicit letter and then put it through the shredder. When I do this sort of thing, I'll set the letter aside in a private place for a day or two, then reread it, then put it through the shredder. Sometimes it's surprising what comes out when you just let yourself start flowing emotions. Sometimes it's not even about the thing you think it is, but your mind will take you where it needs to go, iykwim? Sometimes I go through that process a few times before it feels done. Don't know if something like that might work for you, or if it might be something you are interested in trying. Just an idea...