I may be able to relate as something really crappy (like "takes the cake" crappy) happened to me a year ago. I was super angry for days and concerned about how I would ever get over it. I'll mention what helped me with hopes it might help you too:
1. Venting;
2. Talking it out with a non-provocative person;
3. Complaining;
4. Accepting that it might take time to feel better and that the mind is suppose to naturally recover from anger over time (and not getting angrier because I don't deserve to be angry - angry over being angry);
5. Working on the underlying problem that caused the anger (and processing it);
6. Righting wrongs to the extent possible.