"I was like, what ?"

here's the thing,

Now that my friend was turning 50, I cautioned him that one's semicentennial was a time to start taking things slower. "Just remember what the Romans used to say," I warned.
"What's that?" he said
"You're about to go to L."

A joke from Reader's Digest, by Gene Newman ;)

i read this again again and again, couldn't found wht ths L supposed to mean. im no good at this jokes thing, myb someone Braniac could tll me wht this joke is about ;D haha

.....

L for Loser, L for Life, L for lasagna ? wht the hell ? Gosh