Ever feel like you are beating a dead horse?

Sometimes we all feel as if we are beating a dead horse, though not literally, of course. “To beat a dead horse” means to waste time and energy trying to do something that cannot be done or trying to convince someone of an opinion that the don’t share.

For example, “I was beating a dead horse trying to explain to Grandma that people have walked on the moon. She insists the moon landing was fake.”