Rigorous exercise seems to get me out of any ruts I'm in. I typically hike 5-6 miles x 3 days a week, and throw in a 11-12 mile over strenuous terrain. By the end of that, your mind will clear, your body is exhausted, and you'll rest easy that night.

Other than that, eating well, having plenty of great sex, and interacting with as many people as possible. OH most important, SLEEP, a full solid night of it. Naps are awesome too.