I have a variety of responses to this, so pick your favorite.
The Classic: GMAFBAGFY
The Self-Depricating Bon Jovi Reference: Whoa, we're halfway there! Whoa! Livin on a prayer!
The Wire Reference: The F**k did I do?
The Depressing: Oh look, he's an optimist.
The Insulting Reply: Well, I met your mother long before I was 52.
The Optimist: Hey, I'm doing alright for myself if I'm still getting laid at 52.
The Stupidly Overconfident: When I win the powerball this weekend, it's all coke and hookers, baby. Now who looks stupid?
The On-Topic Reference: Suck it, Trebek.