One thing that motivates me is seeing gradual, measurable improvement.
I started running last year when my roommate dragged me to the gym with him - and I would always be running against my previous times, in my head, and be thrilled about gaining some time here, etc..
I find that weightlifting can get a bit boring, but I have another goal there: pull-ups. I started at 0 and ended up doing 10 or so in a row. Stuff like that made me feel better about my health, my strength, and my attractiveness.
I stopped going to the gym after a while because of some knee problems, and because my life was undergoing and bigger transition. I've been seeing a doctor again for my knee - though I'm not terribly satisfied with him and I might look for another one. And I started going to the gym again, and now I went back from 0 to 3 pull-ups, and soon enough I'll get back to 10, I know it
