In other words, stop being so cocky. You are not as great as you think you are. Sober up in your self-assessment. Watch out for pride. It is the idea of exercising self-restraint.
Youth tend to throw off self-restraint.
Two areas in particular that young men tend to throw off restraint are with sexuality and authority. Guys must discipline themselves and control their passions and thoughts, lest they enter into sinful lust. Younger men also tend to be impatient with established authority. They need to learn to respect their fathers, their elders and all those in authority, as the Bible teaches. While older women were to train the younger women, Paul gave Titus the task of encouraging the young men.