Believe that you're shaping up (so you don't ship out)

The mind is a powerful thing, and that is true even when it comes to working to improve the physical condition of your body. In a recent study that compared participants who had been told they were out of shape to those who had been told they were in good shape (by a believable source after testing had been done), those who were told they were in worse shape reported feeling more fatigued than the other group -- which not only reported feeling less tired, but also had better over-all feelings of well-being. So people who believe they are healthier and making progress have more positive energy and more often ignore feelings of fatigue -- which of course means they're more likely to stick to their workouts.

Sounds like there's a case to be made for "believe it, and it will happen."