at wits' end

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.
See also: end
Farlex Dictionary of Idioms.

at (one's) wits' end

At the limit of one's mental resources; utterly at a loss.
See also: end
American Heritage® Dictionary of the English Language, Fifth Edition.
See also:
  • at (one's) wits' end
  • at one's wit's end
  • at wit's 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