"Snap out of it!"

The Movie: Moonstruck, 1987 (John Patrick Shanley, screenwriter; Norman Jewison, dir.)
Who says it: Cher as Loretta Castorini, a widow disillusioned with love
The context: Loretta smacks Ronny Cammareri (Nicolas Cage), her brother’s fiancé, when Ronny tells Loretta he loves her.
How to use it: To shock someone out of a fantasy, or put a stop to embarrassing sentimentality. Don't actually slap anyone, though.

I need to snap out of it. The other day I stood paralyzed in front of the dairy case, thinking that if I bought the half-gallon of skim milk (instead of the quart), it would be the last jug of milk I’d buy in Los Angeles. Had I not been surrounded by people, I’d have smacked myself and shouted this. Since my health insurance doesn’t cover mental illness, I let the opportunity pass.

Bye-bye, Alta Dena Dairy.