The more you talk, the less they hear. Say it in a word.
You know when you're lecturing. You can see it on your child's face. Or in the eye-rolling. Or in the sigh. They know what's coming after the first few sentences, proabably after the first few words. But you keep going because now they're being disrespectful and you're going to make your point if it's the last thing you do! You've been there. I've been there. Maybe you got that look or sigh from your partner, too.
You've lost this round, in more ways than one. You're frustrated and they've mentally checked out. Whatever lesson you're trying to impart is now out the window. Nagging doesn't teach responsibility... it teaches your child to avoid you and all the things you want him to do. When they are older, your kids will say the lecture is one of the things they'll never do to their own children!
With teens, and most other people, less is more. You don't make your point any better by saying the same thing over and over or in different words. Say it in a word or two. Your laundry. Be home by 11:00. No phones at the table.
Message delivered. Time to move on.