Ah, to be twenty again. I smacked about a dozen or so cars in my first few years of urban cycling, then ceased the practice when I decided to stop riding angry. It didn't seem to accomplish much beyond feeding my sense of furious righteousness, which was preventing me from being able to relax and enjoy the ride. At some point I got tired of feeling like I was girding for battle every time I threw a leg over the bicycle; the same point that riding my bike started causing me more stress than driving my car.

I still get irritated when someone steals my right of way or forces me to avoid a collision that they almost caused, but irritation is easy to shrug off. Anger stays with you, it taints the rest of your day. I try not to get angry unless I've been struck or run off the road; and even then I'm not smacking the car, I'm calling the cops.