At 88, I remain a competitive runner, always sprinting the last hundred yards of a race to cross the finish line with nothing left to give. The finish line of my life is drawing close, and I hope to reach it having given the best of myself along the way. I’ve been training my body to meet the demands of this final stretch. But, I wonder, should I have asked more of my mind?

I have no trouble taking my body to a gym or starting line. I’ve done a good job convincing myself that if I didn’t exercise, I would unleash the many predators that seek their elderly prey on couches, but not on treadmills. The more I sweated, the more likely it was my internist would continue to exclaim, “Keep doing what you’re doing, and I’ll see you next year.” It was my way of keeping at bay the dreaded: “Mr. Goldfarb, I’m afraid I have some bad news.”

My mind, on the other hand, seems less willing to yield to discipline, behaving as though it has a mind of its own. I have dabbled in internet “brain games,” solving algebraic problems flashing past and rerouting virtual trains to avoid crashes. I’ve audited classes at a university, and participated in a neurofeedback assessment of my brain’s electrical impulses. But these are only occasional diversions, never approaching my determination to remain physically fit as I move deeper into old age.

Despite having many friends in their 70s, 80s and 90s, I’ve been far too slow to realize that how we respond to aging is a choice made in the mind, not in the gym.