He was at his wits' end, having worked a year for nothing.
他哭不得笑不得,一年的气力白费了。
《新英汉大辞典》
2
You are at your wits' end and have begun to dread meal times.
你为此绞尽脑汁并且开始害怕吃饭时间的到来。
3
Even if the person may be at his/her wits-end handling the individual, just observing from a third party's point of view can give you insights on how to manage.