The next two verses were both in Titus 2… so I thought I would copy the whole chapter:
Doing Good for the Sake of the Gospel
” 1 You, however, must teach what is appropriate to sound doctrine. 2 Teach the older men to be temperate, worthy of respect, self-controlled, and sound in faith, in love and in endurance.
3 Likewise, teach the older women to be reverent in the way they live, not to be slanderers or addicted to much wine, but to teach what is good. 4 Then they can urge the younger women to love their husbands and children, 5 to be self-controlled and pure, to be busy at home, to be kind, and to be subject to their husbands, so that no one will malign the word of God.
6 Similarly, encourage the young men to be self-controlled. 7 In everything set them an example by doing what is good. In your teaching show integrity, seriousness 8 and soundness of speech that cannot be condemned, so that those who oppose you may be ashamed because they have nothing bad to say about us.
9 Teach slaves to be subject to their masters in everything, to try to please them, not to talk back to them, 10 and not to steal from them, but to show that they can be fully trusted, so that in every way they will make the teaching about God our Savior attractive.
11 For the grace of God has appeared that offers salvation to all people. 12 It teaches us to say “No” to ungodliness and worldly passions, and to live self-controlled, upright and godly lives in this present age, 13 while we wait for the blessed hope—the appearing of the glory of our great God and Savior, Jesus Christ, 14 who gave himself for us to redeem us from all wickedness and to purify for himself a people that are his very own, eager to do what is good.
15 These, then, are the things you should teach. Encourage and rebuke with all authority. Do not let anyone despise you.”
Another reason why it is important to learn self-control: as a witness to others.