What does Proverbs 29:11 mean?

Self-control is one of the biblical marks of godly wisdom (Proverbs 10:19; 25:28). The ability to control one's speech is especially valuable (Proverbs 17:27). A "fool" is someone who ignores godliness and common sense (Proverbs 8:32–36). Emotions are volatile (Proverbs 16:32) and need to be restrained by a reasoned mind (Romans 12:2). A foolish person lets his emotions control him.

This verse uses an uncommon Hebrew phrase associated with stopping the motion of a liquid, such as waves in the sea or water sloshing in a bucket (Psalm 65:7; 89:9). This captures the difficulty of calming one's own temper and holding in angry words (James 3:2–5). The solution to a lack of self-control is God's influence through the Holy Spirit (Galatians 5:22–24). One of Jesus' demonstrations of power was to calm dangerous waves with just a word (Mark 4:39–41). What's impossible for people (James 3:8) can be done through God's power (Luke 18:27).

Although the disciples James and John were not fools, they acted like fools by asking Jesus for permission to call down fire on Samaritan villages which rejected Jesus. They asked: "Lord, do you want us to tell fire to come down from heaven and consume them?" (Luke 9:54). Jesus responded by rebuking them. The two disciples were the "Sons of Thunder" (Mark 3:17), but during His ministry Jesus transformed them into loving disciples.