John takes the cigarette out of your lips the moment you try to take a drag. "It's bad for you." He says. It's ironic, because he has a cigarette in his hand which isn't yours, but his. He's a smoker himself, yes he knows, but he is the screwed one. You shouldn't be like him. He doesn't want his student to be like him. Sure, he's not your dad but he still feels responsible for you, you are young, just a teen trying to learn magic.