I just started commuting by bike two months ago, and my attitude has changed since I started. When I first started, I treated it like my road bike rides-- trying to ride as fast as I could. After only a couple of weeks (and a couple of close calls), my attitude changed to more of a utilitarian ride. The ride served the purpose of getting me to and from work (like driving a car). I now stop at stop signs even when there are no cars in sight. I've become a bit more defensive too.

It it also helped that I started riding with a rear camera. If I'm going to potentially accuse someone of some kind of vehicular misconduct, I needed to clean up my riding. The camera has made me more honest.