Something that can make a defining difference in one's life is drive.

Drive might not make one happy, but it helps make one be the best that they can be and enhances the prospect of success (and happiness).

I didn't have much drive when I was coming up and there were a number of disappointments and failures along the way. At some point, however, I'd had enough and those experiences help fuel the drive which I still have to this day. 

One can be driven to triumph by will. Or in the words of Nike: Just do it!  Just find a way to get it done.

Drive, he said.  Put me in Coach, I'm ready to play!