[SlowTao]

I forgot who said it but they had the theory that the way to stay sharp is to take on new mental tasks that create new though patterns.

You know when you are learning something and you get to that point where it is kind of a strain. That feeling that is kind of tense, exhausting but intriguing, all because you are about to get that thing. It is the transition from something being purely cognitive and moving into behavior intuition, like playing an instrument.

That is the thing that, in part, is keeping you sharp.

I say in part because don't forget your physical health, diet and social health. They all contribute.