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." Every good thing we do is the fruit of the Spirit’s work in our lives.

Self-control is the ability to control oneself. It involves moderation, constraint, and the ability to say “no” to our baser desires and fleshly lusts.

One of the proofs of God’s working in our lives is the ability to control our own thoughts, words, and actions. It’s not that we are naturally weak-willed. But our fallen nature is under the influence of sin. The Bible calls it being a "slave to sin” (Romans 6:6). One definition of sin is "filling a legitimate need through illegitimate means." Without the power of the Holy Spirit, we are incapable of knowing and choosing how best to meet our needs. Even if we knew what would be best, such as not smoking, another need, like comfort, would take precedence and enslave us again.

When we are saved by Christ’s sacrifice, we are free (Galatians 5:1). That liberty includes, among other things, freedom from sin. “Our old self was crucified with him so that the body of sin might be done away with, that we should no longer be slaves to sin” (Romans 6:6). Now, as the Spirit gives us self-control, we can refuse sin.

Believers need self-control because the outside world and internal forces still attack (Romans 7:21-25). Like a vulnerable city, we must have defenses. A wall around an ancient city was designed to keep out the enemy. Judges at the gates determined who should be allowed in and who should remain outside. Soldiers and gates enforced those decisions. In our lives, these defenses might include setting standards for our lives, having a fellow-believer that we meet with who keeps us to those standards, meeting with other believers, keeping a journal of successes and failures, close confession of sin, and meditating on the life-giving Word of God. We don’t exhibit self-control if we continually to do with that which would enslave us.

Self-control naturally leads to perseverance (2 Peter 1:6) as we value the long-term good instead of the instant gratification of the world. Self-control is a gift that frees us. It frees us to enjoy the benefits of a healthy body. It frees us to rest in the security of good stewardship. It frees us from a guilty conscience. Self-control restricts the indulgence of our foolish desires, and we find the liberty to love and live as we were meant to.  (From: https://www.gotquestions.org/fruit-Holy-Spirit-self-control.html)

 

Finally, self-control is essential in the missionary’s life.  It has to do with discipline, focus on each day moving forward in accomplishing God’s call on our lives, refusing to give in under the stresses and difficulties of life, and determination to please God.