be laughing on the other side of your face

be laughing on the other side of (one's) face

To be experiencing a drastic change in one's emotions, often in a short span of time. A: "I thought your mother was happy that we're getting married." B: "Me too, but now she's laughing on the other side of her face, and I get an angry phone call from her every day."
See also: face, laugh, of, on, other, side
Farlex Dictionary of Idioms.

be laughing on the other side of your face

BRITISH or

be laughing out of the other side of your mouth

AMERICAN
If you say that someone will be laughing on the other side of their face, you mean that although they are happy or successful now, things are likely to go wrong for them in the future. The league leaders will be laughing on the other side of their faces if they lose tomorrow. You'll be laughing on the other side of your face when you fail all your exams and can't get a job. When this game is over, Charley, you'll be laughing out of the other side of your face.
See also: face, laugh, of, on, other, side
Collins COBUILD Idioms Dictionary, 3rd ed.
See also:
  • be laughing on the other side of (one's) face
  • be laughing out of the other side of (one's) mouth
  • laugh on the other side of (one's) face
  • laugh on the other side of (one's) mouth
  • laugh on the other side of your face
  • laugh out (of) the other side of (one's) mouth
  • laugh out of the other side of mouth
  • laugh out of the other side of one's mouth
  • laugh out of the other side of face and laugh out of the other ...
  • laugh out (of) the other side of (one's) face