Laugh out of the other Side of Your Mouth
To be made to feel sorrow, annoyance or disappointment after you felt happy;
to cry at a change in luck after experiencing some happiness.

This saying was being used in the 17th century. It might not seem to make much sense since when a person
laughs he or she does it from both sides of the mouth. The words “the other side,” however, indicate the other
side of happiness (sadness), so the idiom suggests that by laughing on the other or wrong side of your mouth
or face, your fortune has gone bad and your moment of happiness is over.
Thrilled a month ago to receive a raise, he was laughing on the other side of his mouth
when he was let go last week.
(From the “Dictionary of Idioms,” Marvin Terban, Scholastic Inc., publisher, 1996)