Take breaks between big projects. Burnout puts your mind and body in a weakened state, so avoid jumping from one stressful, time-consuming project to the next in order to give your mind and body a chance to recover.
Socialize outside your professional group. This can provide fresh perspectives, stimulate new ideas, and help you discover previously undiscovered resources.
Reinforce effort, not outcome. Not even the best players hit home runs every time they get up to bat. Remember to reinforce yourself for trying rather than only for the end result.
At the end of the day is all about BALANCE. I'm personally working on this right now... and I imagine it will be something that can always be improved.