…but hospitable, loving what is good, sensible, just, devout, self-controlled
Titus 1:8 (emphasis mine)

To be self-controlled is to practice restraint.

It can relate to physical desires:

But if they do not have self-control, let them marry; for it is better to marry than to burn with passion.
1 Corinthians 7:9

A successful athlete must practice self-control in all areas of life. In the same way, the Christian leader must exercise the same level of self-control if they are to accomplish God’s purposes.

Everyone who competes in the games exercises self-control in all things. They then do it to receive a perishable wreath, but we an imperishable. Therefore I run in such a way, as not without aim; I box in such a way, as not beating the air; but I discipline my body and make it my slave, so that, after I have preached to others, I myself will not be disqualified.
1 Corinthians 9:25–27

It is the Spirit of God that makes it possible for His children to have this restraint.

But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, self-control; against such things there is no law.
Galatians 5:22–23

John MacArthur states well the responsibility of the elder:

The self-controlled pastor walks with God in the integrity of his heart. He has the continuing grace of God working in his life to the degree that he is spiritually mature and morally pure. He should be able to say with Paul, “Our proud confidence is this, the testimony of our conscience, that in holiness and godly sincerity, not in fleshly wisdom but in the grace of God, we have conducted ourselves in the world, and especially toward you” (2 Cor. 1:12).

1 MacArthur, J. F., Jr. (1996). Titus (pp. 42–43). Chicago: Moody Press.