A quote from Robert Heinlein: Never try to teach a pig to sing; it wastes your time and it annoys the pig.

Usually applied to someone that has a character flaw or annoying habit they will never change because they simply aren't able to.
A person with bad hygiene - you tell them they stink but they don't really care.
"Getting you to clean your room is like teaching a pig to sing; it's a waste of my time and all it does is annoy you."
by BigRed60 August 1, 2009
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Don’t try to teach a pig to sing; it doesn’t work and it annoys the pig. Basically don’t bother teaching a stubborn person a life lesson if they’re not gonna learn from their mistakes anyway. They’re still going to keep making the same stupid mistake and expect a different result every time.
Due to Nicole’s stupidity for the last decade with the “edgy” ex-boyfriends and getting arrested multiple times, she’s never going to learn to grow the fuck up and never learn lessons in life. Don’t try to teach a pig to sing.
by rosenovarocks August 14, 2021
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