What has gotten harder for you as you've gotten older?

What’s prompted this question is my struggle to understand and remember some French grammar rules now that I’m studying the language again. Things that I think would have been easy for me to learn and remember are just not going in the way they would have.

What about you? What things – either physical or mental – do you struggle with now that you are older?

(Putting this in General because I’d like to keep the discussion somewhat focused but humor is welcome too.)