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Related to lose marbles: part and parcel, Look before you leap, up to par, worse for wear
lose (all) one's marblesand lose one's mind
Fig. to go crazy; to go out of one's mind. What a silly thing to say! Have you lost your marbles? Look at Sally jumping up and down and screaming. Is she losing all her marbles? I can't seem to remember anything. I think I'm losing my mind.
lose your marbles
to start forgetting things, behaving strangely, or becoming mentally ill I haven't lost my marbles yet. She's begun to lose her marbles, and there's nothing we can do.
lose your marbles(informal)
to start acting in a strange way and forgetting things I may be old, but I haven't lost my marbles yet. (informal)