Christianity is a religion that emphasizes self-control. Jesus said - "If anyone desires to come after Me, let him deny himself, and take up his cross, and follow Me" (Matt. 16:24). To deny self requires subjecting one's will to that of God. This means that the disciple needs to have the attitude the Lord expressed when He said - "Father, if it is Your will, take this cup away from Me; nevertheless not My will, but Yours, be done" (Luke 22:42). To deny self certainly requires control of one's desires.
Sadly, there are many in this world who have never learned to practice this virtue. Paul spoke of the unmarried who might not be able to exercise self-control (cf. I Cor. 7:8,9). When the apostle addressed Felix he "reasoned about righteousness, self-control, and the judgment to come, Felix was afraid and answered, 'Go away for now; when I have a convenient time I will call for you'" (Acts 24:25). He was right to be afraid because his life was one of wickedness and immorality. Proof of this is seen in the next verse where we learn that he was hoping Paul would offer a bribe to release him from custody. His thoughts were evil and it appears he did not desire to control himself.
Christians are commanded to develop self-control in their lives (cf. II Pet. 1:5-7). Doing such makes one able to bear fruit in the Lord. Failing in this regard makes the person vulnerable to false teachers who turn the grace of God into a license to sin (cf. II Pet. 2:18,19; Jude 4). Peter said that developing self-control is intimately connected to the knowledge of the Lord (cf. II Pet. 1:8). Thus, it should come as no surprise that self-control is included in the fruit of the Spirit (cf. Gal. 5:22,23).
What is necessary to develop self-control in a person's life? For starters, one needs to learn to think about what he thinks about! Proverbs 4:23 teaches us - "Keep your heart with all diligence, for out of it spring the issues of life." Obviously, the word "heart" in this verse is not referring to the blood-pumping organ in the chest but the mind of man. What a person thinks about will determine what kind of person he is or will become (cf. Prov. 23:7). Jesus put it this way - "For out of the abundance of the heart the mouth speaks" (Matt. 12:34).
The old saying, "garbage in, garbage out" is very true. If a person wants to live a holy life with self-control, he must fill his mind with things that are true, noble, just, pure, lovely, of good report, and praiseworthy (cf. Phil. 4:8). Paul instructed Christians to meditate upon those things. In other words, fill your mind with the good and it will push out the bad.
Self-control is developed when a person learns to control his thinking. Far too many never reflect on their thoughts, and consequently, they fail to change for the better. They are at the mercy of the bad thoughts in their minds. The Lord taught that overt sins arise from the motives that prompted the action. For example, adultery is a sin that arises from lust in the heart (cf. Matt. 5:27,28). To prevent adultery, the lust must be removed. That is why Jesus said - "If your right eye causes you to sin, pluck it out and cast it from you; for it is more profitable for you that one of your members perish, than for your whole body to be cast into hell" (Matt. 5:29). He did not mean that a person should literally pluck out his right eye. Instead, He was teaching that one needs to control his thoughts--even if it is painful or costly to do such! The impure must be cut out and replaced with holy and righteous thoughts. This is the heart of self-control.