There is a great New York Times magazine article on Jerry Seinfeld’s work ethic. Here is a great quote on how he keeps himself focused and sharp.
“I read an article a few years ago that said when you practice a sport a lot, you literally become a broadband: the nerve pathway in your brain contains a lot more information. As soon as you stop practicing, the pathway begins shrinking back down. Reading that changed my life. I used to wonder, Why am I doing these sets, getting on a stage? Don’t I know how to do this already? The answer is no. You must keep doing it. The broadband starts to narrow the moment you stop.”
It gives new meaning to the old saying, “If you don’t use it, you lose it!”.