To experience a reversal or drastic change in one's emotions or fortunes, especially from happiness to a negative emotion, often in a short span of time. A: "I thought you were looking forward to being closer to your mother." B: "I was, but having her calling over every single day has me laughing out the other side of my face." They'll be laughing out of the other side of their faces when they realize how much they'll have to pay in late fees.