The thing about anger is that it clouds your judgment and takes your eyes away from the things that matter. It eats away at your soul and steals your joy and whatever happiness you have going for you.
It is indeed foolish to dwell in anger because you are closed to the possibilities and opportunities life opens up for you everyday. It is wisdom to get over yourself and your reason to be angry because 90% of the time, the recipient of your anger has moved on to other things while you remain in pettiness and boiling rage.
Easier said than done, I know, but make the decision to look beyond the situation and let go of the anger. Nothing should be that important to steal your joy and piece of mind.