There are a bunch of aphorisms that people routinely get wrong, frequently by leaving something out that changes the meaning significantly.
"I could care less." - should be - "I couldn't care less." because you clearly want to state you don't care about something.
"Pull yourself up by your bootstraps." - Originally meant something that is simply impossible, because have you ever tried to pull your feet out of mud by yanking on your boots alone?
"Blood is thicker than water." - Full statement originally was "The blood of the Covenant is thicker than the water of the womb." Means exactly the opposite of what people use it for.
"The customer is always right." - People who like to use that expression either don't know, or don't want you to know, the rest: "... in matters of taste." So the customer is always right, unless they're wrong.
... and so on.