collapse after one setback 一蹶不振

“一蹶不振”，汉语成语，意思是一跌倒就再也爬不起来（unable to get up after a fall），比喻遭受一次挫折以后就再也振作不起来。可以翻译为“collapse after one setback；never be able to recover after a setback”。

例句：

我想这个决定对他是个沉重的打击，从此以后他一蹶不振。

I think the decision was a bitter blow from which he never quite recovered.

这场比赛要么使他一举成名，要么使他一蹶不振。

This competition will either make him or break him.