You need to exercise your brain as if it were a muscle. You’ve heard the stories of the dangers of retiring without having a plan for how to fill your time. The stories are true, and the science is there to prove it. Most aspects of work, even the com- mute, the interaction with others, and the daily challenges, are stimulating. When you retire, if you don’t build in challenges for your brain and body, then you can suffer physical and even mental decline. Studies also find that the more intellectually stimulating the job, the less likely it is that Alzheimer’s will strike.