I found a great list of quotes on why runners run here. Check it out for some inspiration.

This one is one of my favorites:
A winner is someone who sets their goals, commits themselves to those goals and then pursues their goals with all the ability that is given to them. That requires someone who believes in themselves, who will make self sacrifices, work hard, and maintain the determination to perform at the best of their ability.
– C. Leeman Bennett

And one more reason to love Scott Adams, creator of Dilbert:

Why aren’t you signed up for the 401K?
I’d never be able to run that far!

Thought Provoking:

My feeling is that any day I am too busy to run is a day that I am too busy
 – John Bryant