Proverbs returns to the theme of self-control with striking frequency because the writers understood what modern psychology has confirmed, the capacity to govern oneself is the foundation of every other capacity.
"Whoever is slow to anger is better than the mighty, and he who rules his spirit than he who takes a city."
— Proverbs 16:32, ESV
The comparison is deliberate. Taking a city in the ancient world, the ultimate demonstration of military power, is described as less impressive than ruling your own temper. The internal victory is harder and more valuable than any external conquest.
Galatians 5:22-23 lists self-control as a fruit of the Spirit, not a technique to be learned, but a quality that grows from surrender to something larger than your own appetites. This is the counterintuitive truth of this trope: the mastery you are seeking does not come from trying harder. It comes from yielding more completely to the one who designed the power in the first place.
A humorous and poignant spiritual lesson is found in Luke 9. James and John were two of the twelve disciples of Jesus. They were brothers who spent many close moments learning directly from Jesus. They had had success and their faith was growing strong. But this chapter of Luke has them asking about which of His followers is the greatest. They then tried to stop outsiders from doing their same work casting out demons. Then finally, in verses 51-56, when they experience rejection from a Samaritan village James and John ask Jesus if they can call down fire on those people. They know they have access to the power of God, but they clearly have a lot still to learn.
David demonstrated power both under control and how it can be abused. In 1 Samuel 24 Saul, along with 3000 men, is pursuing David and his men. Saul stops for a restroom break in a cave. Unbeknownst to him, David and his men are hiding deeper in the cave. The opportunity amazes them, but David restrains himself to cutting off the corner of Saul’s robe. David feels bad afterward that he even did that much harm to King Saul. But David is able to show Saul that he could have harmed him, but chose not to.
In a more famous later story recorded in 2 Samuel 11, David abuses his power. David was a warrior, but he chose to not go out to fight with his men. Instead he was idle in Jerusalem. From the roof of his palace, he spotted a very beautiful woman bathing. Bathsheba, the woman was the wife of one of David’s soldiers. David had her brought to him and got her pregnant. In an effort to cover this up, he tried to get her husband to come back and sleep with her. But Uriah, her husband, was an honorable soldier and refused. So David set him up to be killed. Later in chapter 12, David’s friend Nathan powerfully illustrates and opens David’s eyes to how he has abused his power. It is hard to call out someone in such a powerful position, but Nathan’s rebuke was effective.