Yeah, I agree with Evan and The Decline. Fear of failure or consequences is really the only thing that truly motivates me. I did learn in grad school that the "just do it whether you want to or not" thing does work, just not all the time. Depends on how unpleasant it is.
Getting the unpleasantness over first doesn't work for me. I get the easy/fun stuff done, and then I feel like I've actually accomplished something. Then there's less stuff to do, making it more likely I can force myself to do the stuff I don't like.