As we age, we often experience difficulty understanding complex arguments, completing math problems, and figuring out visual-spatial puzzles. While sometimes these issues are a sign of early dementia, more often they are simply the result of mental inactivity—that is, people who experience these problems haven’t been exercising their brain in these particular areas. Maintaining mental acuity is like training to be a professional athlete; you must pursue it vigorously. The future results are too important for this to be a half-hearted venture. The key is training and practice. You must treat your brain like a muscle, giving it a workout on a regular basis. Instead of picking a by-the-numbers murder mystery, read a more complex philosophical tome. Use a map instead of GPS. Troubleshoot your computer’s error message yourself instead of hiring someone else to fix it. Your brain may complain but you’ll be glad you did the heavy mental lifting.