A high school couple, who met a week ago, are hanging out alone at the girl's parents' house.
She says: "We got the house to ourselves for the next few hours.  Let's take advantage of it and have sex."
"No," he says, "I want to save myself for marriage."
The girl is kicking herself: "Why did I ask him that?  He wants a serious relationship; now I don't know what he thinks of me."
The guy is kicking himself: "I knew I was going to be alone with her; now why didn't I wear clean underwear?"

Moral of the story:
Never leave home without clean underwear