Poor grades and poor life-choices is symptomatic of lack of discipline. The Navy (or any other of the armed forces) won't "teach" you discipline - they'll rub your nose in it until you either develop it or, should you choose to continue your poor choice way of thinking, you'll become someone no one trusts to do the job you're given to the best of your ability. Yes, a good authority figure will help you "learn" to become disciplined but that is a hard road to walk down. It's not a matter of semantics. It's something you have to bring to the fight. That authority figure will just help you hone it. It's a "choice" you have to make for yourself. Discipline can be viewed as the striving for perfection. Good enough is the enemy of perfection. As long as you settle for "good enough" in your life choices, discipline will not be one of your skills.