1. No bigger motivator to run fast than a dozen guys sitting at the foot of your driveway doing roadwork with traffic held up on either side.
2. No better motivator to run further than knowing that same group of guys will still be there when you get back... Unless you can manage to run long enough (I couldn't).
3. Make sure you have a good playlist to keep your mind off your physical anguish.
Some favorite pick-up-the-pace songs (links are to the official music videos):
Any must-have songs you love that I should add to my Run! playlist?