It's from the 11th episode of the 10th season of Friends. Here is the context:
Roy: What's the matter? You never saw a 50 year old stripper cry before?
Phoebe: You know, it's fine. We'll pay you.
Roy: No, no, you're right. Who am I kidding? I should have hung up that breakaway jockstrap years ago. What am I gonna do? I mean, this has been my life for thirty two years. Taking my clothes off in front of people is all I know.
I am sure that's some kind of joke. I can't seem to get it.