Whenever someone who knows my age brings up my age I have two standard replies:

1) "It beats the alternative"; and for people who bring up MY age very often

2) "Clearly one of us has an issue with getting older."

I hate the physical degradation of getting older. Everything else is super-cool. So I try to be the best physical version of me that I can be based on age, work, etc. and then just live the rest of my life like I have since I was in my 20s and had enough money to do anything.

What interests me changes over time. For me, the whole purpose of life is learning and growing. I won't stop as long as I'm vertical.