What motivates me:
1. I feel like I'm 15 years-old again when I'm on my bike... when I'm not climbing, at least.
2. I love the idea that I'm getting from point A to point B with only my power. The bike may make me significantly more efficient, but it is still my power.
3. Commuting to work (two days a week) is green and refer back to # 2 as well.
4. I don't want to die young.
5. It's my quiet time/ alone time when I ride solo.
6. The comradery when I ride with a group.
And that's just off the top of my head. Enjoy.