Tonight was going to be a typical Friday for Duke. He'd have a few beers, meet someone, and - before the night was over - his cherrybuster would deflower anothervirgin ass.
When you ruin somebody's day by telling them some really bad news or make them do something really horrible, usually the receiving person is in a very good mood before said action happened.
person 1: I just won a scratch off ticket.
person 2: Your dog just got hit by a car.
person 1: Man, you just shit in my cherrios!