My problem is that my enthusiasm is sure to peter out. In addition, I run several businesses, work out twice a day - and still have to squeeze in time to travel. Many people begin exercise programs with enormous enthusiasm, then lose it over time. The excuse I hear most often is they're not losing weight or seeing results fast enough. Remind yourself you are getting benefits - improved mood, energy and stamina that you may not see yet.
Motivation comes from within.
One day I misplaced my cassette. I had to hear that song, but it wasn't there. Instead of falling to pieces, I told myself I would be just as motivated without that music, and I was. I learned there would be times when there wouldn't be anybody or anything around to motivate me, so I had to be self-motivated. For me, the biggest motivation is having goals.