Overheard in new york

A conversation in a NYC coffee shop at 7.30 on a Sunday morning between a customer (female in her early twenties) and a clerk (female in her early thirties).

Customer: You are so friendly and happy, how do you do that this early in the morning?

Clerk: I got a good night's sleep; I went to bed at eleven.

Customer: Oh my God! How did you do that?

Clerk (still smiling, but with an ever so sightly condescending look): When you work all day you get real tired, you know.