be at the end of your tether

Từ điển Oxford Advanced Learner 8th

be at the ˌend of your ˈtether idiom
(BrE) (NAmE be at the ˌend of your ˈrope)to feel that you cannot deal with a difficult situation any more because you are too tired, worried, etc
•You'd better let her know you're safe. She's at the end of her tether.
Main entry: ↑end_idiom