Idiom: Beating a dead horse
Examples: 1. Joe moved to a new city, but his mother was not happy about it. She kept calling and asking how he could do this to her. "Stop beating a dead horse, Mom," he said. "I've already moved."
2. Laura couldn't stop talking about her ex-boss after she was fired. Finally, her boyfriend told her, "Stop beating a dead horse. The situation has ended. Let's talk about other things."
3. Sheila couldn't believe that she got a "B" in her math class. She explained to her father over and over again that she really deserved an "A." Finally, her father replied, "Sheila, stop beating a dead horse. Study harder next time so that you can get an "A" in your next math class.
What does "beating a dead horse mean?
It means continuing to talk about a situation after it has ended and the talking will not do any good.