at (one's) wits' end

Related to at (one's) wits' end: all thumbs, rises with the lark

at (one's) wits' end

In a state of distress because one has no more patience or mental stamina, often after having dealt with some kind of problem or difficult situation. The baby's been crying for hours, and I'm at my wits' end! I'm already at my wits' end, so if this train gets delayed too, I'm going to scream.
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Farlex Dictionary of Idioms.

at one's wit's end

Fig. at the limits of one's mental resources. I'm at my wit's end with this problem. I cannot figure it out. Tom could do no more. He was at his wit's end.
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McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

at one's wit's end

Also, at wits' end. Completely puzzled and perplexed, not knowing what to do. For example, I've tried every possible source without success, and now I'm at my wit's end. This idiom, which uses wit in the sense of "mental faculties," appeared in Piers Ploughman (c. 1377).
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The American Heritage® Dictionary of Idioms by Christine Ammer.

at your wits' end

COMMON If you are at your wits' end, you are extremely worried about a serious problem that you have tried hard to solve but cannot. Josh became very difficult after his father's death: he was rebellious and rude, and refused to go to school. I was at my wits' end. We row all the time and I'm at my wit's end.
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Collins COBUILD Idioms Dictionary, 3rd ed.

at (one's) wits' end

At the limit of one's mental resources; utterly at a loss.
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American Heritage® Dictionary of the English Language, Fifth Edition.
See also:
  • at one's wit's end
  • at wit's end
  • at wits' end
  • at your wits' end
  • be at (one's) wits' end
  • be at your wits' end
  • the patience of a saint
  • the patience of a saint/of Job
  • wit's end
  • up against it/the wall