Well my main motivation is my physical and mental well being. I don't HAVE to ride the whole 60 mile round trip commute unless I want to, since my wife and I work in the same office so I can ride in and put the bike on the rack for the drive home, or vise versa.
I've lost about 25 lbs this year and am actually looking slim for the first time in years. I'm in the battle to loose the dreaded last 10 lbs. Commuting by bicycle 3 times a week is my main workout, which I supplement with some light weight training and calisthenics on my off days.
And then there's the quality mental ME time for 1.75 hrs in the morning and 2 hrs in the evening on those days I ride. Did I mention my wife and I work in the same office? Well, sometimes jumping on the bike instead of into the car for the ride home is just the right thing to do!
DanO