Concentration and practice. If you are moving, concentrate on the moving. When you were younger, movement was natural and in the background. Older, you need to focus...

Do you take any supplements or medicine to maintain cognitive abilities?

Sort of. It is not uncommon with age to lose the ability to efficiently breakdown and/or absorb B12. A B12 deficiency can mimic the physical and mental symptoms of the more serious neurodegenerative diseases like Parkinson's. Definitely not fun. I take a supplement that provides roughly 100k of the RDA every day...

psilocybin mushrooms, for one, help hone mind-body coordination.