A man walks into a bar and sees a sign that says "Free drinks for life, just pass the challenge."
Intrigued, the man asks the bartender about the challenge. The bartender explains that the challenge is to down 10 shots of tequila in a row without making a single face.
Feeling confident, the man agrees to take on the challenge. The bartender lines up 10 shots of tequila and the man starts drinking them one by one. He grimaces a little at the taste but manages to down all 10 shots without making a face.
The bartender is impressed and congratulates the man on completing the challenge. He hands him a card that says "Free drinks for life" and tells him he can redeem it any time he wants.
The man is ecstatic and starts coming to the bar every day to claim his free drinks. But after a few weeks, the bartender starts to notice that the man is only ever ordering water.
Curious, the bartender asks the man why he's not taking advantage of his free drinks. The man replies, "Well, I realized that if I'm going to be drinking here for life, I'd better pace myself."