beat a dead horse

 白忙活

?含義：

To continue to focus on an issue or topic that is no longer of any importance or relevance.

指浪費時間做已經(jīng)不再重要或者沒有任何意義的事情。

?例句：

We've all moved on from that problem, so there's no use beating a dead horse.

我們已經(jīng)解決了那個問題，不要再做無用功了。

?對話：

A: Don't you think you are beating a dead horse?

你不覺的你現(xiàn)在在白忙活嗎？

B: Why, because I'm taking diet pills while never stop binge eating?

為什么啊，就因為我在吃減肥藥的同時還在暴飲暴食嗎？

?額外收獲： 

1）move on：繼續(xù)前進

2）there's no use doing...:沒必要做某事

3）binge eating：暴飲暴食