The Characteristics Of The One Who Is In Christ — He Has Self-Control.
Prov 16:32
He that is slow to anger is better than the mighty; and he that ruleth his spirit than he that taketh a city (KJV)
Self-control, as known as temperance, is the ability to control oneself. It involves moderation, constraint, and the ability to say "no" to our fleshly desires and lusts.
The last characteristic listed in Galatians 5:22-23 as a fruit of the Spirit is self-control. The fruit of the Spirit is the change in our character that comes about because of the Holy Spirit's work in us. We do not become a Christian on our own, and we cannot grow on our own.
Philippians 2:13 says that "it is God who is at work in you, both to will and to work for His good pleasure." One of the proofs of the life of a person who is in Christ is his ability to control his own thoughts, words, and actions. Our fallen nature is under the influence of sin. The Bible calls it being a "slave to sin" (Rom 6:6). That is why people who are not in Christ cannot exhibit self-control. They rather exhibit "sin-control." This is because it is sin that rather controls him.
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However, the person who is in Christ has self-control. He is being influenced by the power of the Holy Spirit to resist anything which is not of God. Believers need self-control because the outside world and internal forces still attack (Rom 7:21-25).
Like a vulnerable city, we must have defenses. A wall around an ancient city was designed to keep out the enemies. It was meant to protect the city against attacks from its enemies. Similarly, self-control is a Christian's wall that protects him from sinful life. So if you lack self-control, you are like a city without walls. The Bible says: "He that hath no rule over his own spirit is like a city that is broken down, and without walls" (Prov 25:28). Know that a city without walls suffers destruction. So also a Christian without self-control suffers destruction in his spiritual life.