Curtains

Behind the curtain's mystic fold

The glowing future lies unrolled

~ Neil Gaiman

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Apparently, "it's curtains for you" come from stage plays when he curtain closes at the end of the play. However, if the play is awful, then you're glad when it's curtains. 

Or if it is Jane Curtain and some of her relatives. And if Jane Curtain and her relatives are nice then "It's Curtains for you" when your friend answers the door, well, that could be exciting and a pleasant surprise.

Language is fun.