don't let the door hit you on the way out

Leave here quickly and directly; don't linger on your way out the door. Used sarcastically to express one's desire to see someone leave. I couldn't be happier that you're leaving the firm, you were a nuisance here anyway. Don't let the door hit you on the way out! If you're willing to work hard and put in the hours I ask, then I want you in my company. If not, well, then don't let the door hit you on the way out, as my grandmother used to say. A: "Fine, then I'm leaving!" B: "You're a real jerk, you know that? Don't let the door hit you on the way out!"