What is the worst advice you heard about being a teacher?

This weekend at a friend’s wedding, I had a former professor tell me to “lower my standards. The kids won’t take you seriously if you expect too much from them. Which is shitty advice from someone who went to a private university with a small class size. During my student teaching I was given classes that had 80% of the students in the non-AP classes failing them. That’s a whole different issue but the professor gave me that advice as well.