In Healthy Body, Unhealthy Mind, an op-ed at The New York Times, Pico Iyer tells how regular doctor visits prompted him to undertake an exercise program as he aged. He recounts a friend's reaction to his news with this brilliant image
I proudly reported this breakthrough to a quiet, slightly older friend. “You’ve never thought of doing this with your mind?” he said, a bit ungraciously, I thought. “Just sitting still for a few minutes every day, to give your imagination a chance to take a walk."
He continues with the discovery his friend's reaction led him to
I was, in short, what I’d call an externalist — a person who’ll exercise great care over what he puts into his body and never think about what he puts into his mind. Who will dwell at length on everything he can see, in order to distract himself from the fact that it’s everything he can’t see on which his well-being depends. Who will fill his head with so much junk that he can’t remember that wolfing down Buffalo wings is not the problem, but a symptom.
A thoroughly satisfying read for me, and an incentive to dust off the Pico Iyer volumes on my shelf.