It is urgent that we understand that if bad health increases, brain skill decreases. This happens at any age. However, it is not the same if we start to take care of our health when we are senior adults than if we start to take care of our health since our childhood. What we can do? Health education will motivate us for sure because if youwe understand the effect of bad habits, it will be easier to replace thembad habits with good habits. Sleep well, reduce stress, do exercise, good nutrition, eliminate smoking, alcohol, and drugs. We need to do aerobic exercise, but also anaerobic exercise. Some research suggest that anaerobic is fundamental. I would say that we need to do both. Besides this, there is research that we need to put our brain outside of our comfort zone. Challenge your brain! Do not play blitz. Only classical chess. Most of chess players have convinced themselves, for convinience, that blitz and classical chess are the same, but they are not. About chess games, I play a daily chessgame, 5+30, on lichess.org. Do not focus on the results. Just play one game per day and analyze it. Try hard to discover and learn from your mistakes. If you have enough financial resources, hire a nutritionist and a chess trainer. You can get online chess lessons for $10 per hour. It is a myth that we cannot improve. If you have time, learn a new language, learn to play a musical instrument, study the great philosophers, and the great mathematicians. It is extremely important to study the last research about the brain and health in general. Subscribe to American Mind, a magazine specialized in brain health. In chess, more important than reading is to solve exercises without time limit. I had the opportunity to listen a lecture from one of the best chess trainers of the world, Ramachandran Ramesh, he emphasized that puzzle exercises are important if you get 100% or you are close. So, quality is more important than quantity. Puzzle rush, it is a very bad idea because, according to Ramachandran Ramesh, you "learn to be mediocre." We need to fight to achieve excellence. Puzzles are extremely difficult and helpful. There are excellent books. Do middlegames and endgames puzzles. I like Maxim Blokh, Mark Dvoretsky, and Steve Giddins books. But, there are fantastic books written by John Nunn, Jonathan Speelman, Jacob Aagaard, Boris Gelfand, Boris Gulko, etc. It is important to do 50% endgames, 50% middlegames. If you have time do as many as possible every day. However, if you do not have good health, your chess ability will decline no matter what you do. Physical and mental health must be your priority! Best of luck!