meaning
To continue wasting time and effort on something that cannot be changed, solved, or improved. It refers to persisting with a pointless discussion, argument, or action after it has become useless.
also
To flog a dead horse
proverb
meaning
To continue wasting time and effort on something that cannot be changed, solved, or improved. It refers to persisting with a pointless discussion, argument, or action after it has become useless.
also
To flog a dead horse