I hear you on that...a few months after my son was born, I was riding my motorcycle home from work and the thought popped into my head "This is really dumb. Any of these cars could just take me out...I've got a little guy depending on me!" Needless to say, I sold the motorcycle.
Speaking of motorcycles though, one very good thing about "defensive driving" for bicycles that I learned from my many years of motorcycle riding was that you have to ride as if you're invisible to the other motorists. Never assume someone can see you. On a motorcycle, one can somewhat counteract your lack of visibility by using sound (i.e. "Loud pipes save lives"), but that's hard to do on a bicycle.
http://bikeblather.blogspot.com/