Educators: In a disciplinary sense, what things have you decided to "let slide"?

I’ve come to the realization after two years at the high school level that if I reprimand teenagers for every little thing, I have no time to teach and I become a nervous wreck.
For instance, I’ve let cussing go unless it’s directed at me (and THAT is not a pretty scene) because it is a losing battle…I just pretend I don’t hear it.
What things have you found are useless to try to correct? Or that you once punished but realized aren’t detrimental to the classroom or learning?