I have a sorta different twist on this topic:

I got interested in cycling; and primarily racing, when someone (am man) I was VERY close to started telling me about his riding and training. I became his encouragement day in; and day out. Then, I decided to get a bike and ride myself. Long and short of it: the relationship is over (not by my choice) and I am still riding like crazy. I am chasing someone all the time. That is quite a motivator for me.

I guess what I am saying is, compete with someone at whatever you do and you'll stay motivated. Get someone who is in the same boat you are in and see who can reach a milestone first or see who can keep up a workout schedule the longest.... compete at something. It is working for me.

Kim