Flogging a Dead Horse.

Also beating a dead horse and so on.

The same is said for the dead marriage, or the effort on a work project that is simply not going to progress.

Flogging a dead horse is an idiom that means a particular effort is a waste of time as there will be no outcome, such as in the example of flogging a dead horse, which will not cause it to do any useful work. - Wikipedia.

To beat a dead horse would be pointless, as it wouldn't be able to go anywhere.

Some people will keep on talking about a subject in the hope that it can change, will change, if only…

But what they are really doing is flogging a dead horse, the chances of the situation changing died a ways back.

To keep talking about a subject that has already been discussed or decided

To waste time and effort trying to do something that is impossible. - Merriam-Webster.

To continue to focus on some issue or topic that is no longer of any use or relevance.
We've all moved on from that problem, so there's no use flogging a dead horse.
OK, Tom, you've made your point. Let's not flog a dead horse.
Waste energy on a lost cause or unalterable situation.
To pursue a futile goal or belabor a point to no end.

- The Free Dictionary.

My mother used to say this one a lot. She would say something like, “There is no point flogging a dead horse.” when she was trying to tell us that the particular effort we were putting into something was not going to change anything.

It has been said that it means that no matter how much effort, time, and your life that you put into whipping a dead horse trying to get it to get up and do what you want it to do, nothing is going to change because it can’t.

The horse is dead, it can’t revive itself, it can’t get back up and try anymore, its had it.

All the best from

James M Sandbrook.

1st of April, 2021.