I found a joke once that involved a man and his donkey taking a walk, but people are demanding to him, and when he tries to satiate their demands, the donkey ends up falling off a cliff, with the punchline being "If you try to please everyone, you might lose your ass."
I know "ass" is slang for both "buttocks" and "donkey" and thus it's a pun, but I don't know what "losing one's ass" means.