To go out the window
When something is no longer applicable or valid, you can say it "goes out the window."
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DefinitionYour turn
When buying a sports car, all practical concerns “go out the window.” When you buy a sports car, you forget about practical concerns like price, fuel economy, and reliability: you buy based on pure emotion. When I go on vacation, my normal diet goes out the window and I just enjoy the food at my destination.