It really depends on what you're talking about. If someone cuts me off at a light, I blow it off quickly, it wasn't personal, who cares? If someone does something intentionally to make me angry, that's a different story. I don't deal in revenge, usually I just ignore it unless they're a real douche, at which point, depending on relative positions, I can make their lives suck, but usually I won't.
I used to get really upset. Now, what difference does it make?