What does a dead horse matter mean?

"A dead horse" refers to a useless or pointless situation or endeavor. The phrase "a dead horse" in this context is a metaphor originating in the practice of horse racing or equestrian sports, where a dead horse is a horse that has died or been euthanized due to injury or illness, and is therefore of no further use for racing or riding.

When applied to other situations, "beating a dead horse" or "flogging a dead horse" refers to continuing to put effort into something that has already failed or become futile, without any chance of success or positive outcome. It implies that further attempts or efforts are unnecessary and unproductive, and that resources, energy, and time would be better spent elsewhere.

The phrase serves as a caution against persisting in fruitless endeavors and encourages letting go of unproductive pursuits or unproductive pursuits or focusing on more promising opportunities. It is a reminder that it may be time to reassess priorities, change strategies, or abandon certain courses of action that have become unproductive.