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

at (one's) wits' end

At the limit of one's mental resources; utterly at a loss.
See also: end