I can never motivate myself to exercise.  I do, however have to get to work every morning, and I can generally motivate myself for that, so since I live about 10 kilometers from work I just jog to work every morning.  Every Monday I take a bundle of work clothes for the rest of the week and drive to work then jog a 10K loop.  The rest of the week I jog from home to work.  I usually get a ride home.  Sometimes I'll ride a bike to work, then leave the bike there at the end of the day and jog home, then the next day jog to work and ride the bike home.  Fortunately I have access to a shower at my office.  I have no will power for exercise, but I do have just enough for commuting.