I recently heard an interview by Kevin Rose of the great magician David Copperfield.
Copperfield made a comment during that interview that resonated with me: “The people that really last (in their chosen field), stay hungry. They stay hungry.” (You can view the interview here: http://www.googleventures.com/foundation).
Copperfield was responding to a question about how he stays energized, fresh, relevant.
When we choose (or allow ourselves) to stop learning, we quickly become irrelevant and marginalized.
The mind, just like our bodies, performs best and most reliably when it is pushed, stretched, challenged on a frequent basis.
It's all about FITNESS - mental, physical, and emotional/spiritual.