Most of you probably heard the phrase "gild the lily", which describes the act of trying to improve something that is already perfect.
What I'm looking for is the opposite of that, is there a phrase/idiom that describes the act of trying to repair something that is ruined beyond repair?
The phrase "beat a dead horse" comes to mind, but to me, it feels like it describes the act of carrying on trying to fix something when it's too late to do so.