be at (one's) wit's end(redirected from be at his wits' end)
be at (one's) wit's end
To be 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 wit's end! I'm at my wit's end, so if this train gets delayed too, I'm going to scream.