That's me as well. Every day I don't drive is 20 pounds less CO2 released by my car. I'm a lot trimmer than I was before I started. Also I find if I've had a bad or busy day, commuting clears my mind before I get home (or sometimes, to work). I also sleep better due to the exercise.

But mainly, it's the environment. Yes, my little bit won't make a difference, but everything starts somewhere, and if the people who care don't do anything, why will anyone? In 50 years when we're in emergency mode, 30 years past tipping point, at least I'll be able to say I did what I could.