mount on a dead horse

• [口]重提早已解决了的问题,炒冷饭,白费口舌

mount on a dead horse的用法和样例：

例句

1. You knew you wouldn't lend me the money and yet,and yet,you let me go on.
   可是，可是你还让我白费口舌。
2. Don't waste energy fussing over a minor matter.
   不要在微小的事情浪费精力。
3. It is a waste of energy arguing with her.
   和她争论是浪费精力。