Jeff at 2009-03-12 22:23:00:
There's a small self-help book out there entitled "Dojo Wisdom for Writers" by a woman named Jennifer Lawler. While it doesn't revolve around screenwriting specifically, it, like Mr. Lawton, spends about 200 pages drawing comparisons of writing to martial arts. One of my favorite "get off your ass and get writing" books ever. Recommended for anyone like me who suffers from terminal procrastination.
I was a student of Tae Kwon Do for about two years and crawled my way up to a green belt. Now, with the sheer head count of children in my house, there's simply no time but I can say that regular jumping, board breaking, and keyoping did wonders for all aspects of my life, writing included.