In The RARE SENSE® Manifesto, I discuss the three major components of overall mind fitness: Orientation, Development, and Maintenance.
Development is how we grow our minds. What can we learn, apply, solve, and create? Learning happens in two ways: academically through acquiring knowledge or by developing a skill. The beauty is that barring a neurodegenerative or physical condition that impairs your movement, you can get smarter and more skilled as you get older. As the adage states, wisdom comes with age. You can pick up something like the piano in your seventies. This starkly contrasts your physical fitness, which eventually degrades regardless of your best efforts to the contrary.
However, you still have to do the work. So, for this exercise, devote some time to a skill. It can be something you already enjoy or an entirely new endeavor. But it must involve your body somehow: playing an instrument, woodworking, archery, juggling, etc. Spend thirty minutes a day trying to get better at it. Create some new neurons and expand your mind.
DISCLAIMER: RARE SENSE® content is not medical advice. Nor does it represent the official position or opinions of any other organization or person. If you require diagnosis or treatment for a mental or physical issue or illness, please seek it from a licensed professional.