Like some of you said, looking in the mirror helps motivate me. I love the fact that I can flex my arm and I actually have something there to show! Some goes for my chest too
Also I went shopping the other day because my clothes were getting so big on me! I used to wear XXL shirts and size 38 shorts/pants, but the shirts I got were all size Medium and my shorts were size 30!
All in all, I have to say that knowing I'm healthy is important too. I used to eat so much junk and drink so much soda and crap like that, but now I eat healthier and exercise often and just feel great.