A dispute also arose among them, which of them was to be regarded as the greatest. And he said to them, "The kings of the Gentiles exercise lordship over them; and those in authority over them are called benefactors. But not so with you; rather let the greatest among you become as the youngest, and the leader as one who serves. For which is the greater, one who sits at table, or one who serves? Is it not the one who sits at table? But I am among you as one who serves.
"You are those who have continued with me in my trials; and I assign to you, as my Father assigned to me, a kingdom, that you may eat and drink at my table in my kingdom, and sit on thrones judging the twelve tribes of Israel.
Luke 22:24–30 (RSV)
We speak of the 'terrible two's' when a child has become mobile and is beginning to use language. It is not uncommon to hear, 'Mine!' and 'I do it!' as they seek to control the world around them. They want to be the ruler of all they survey.
In adult wisdom, we don't allow them to rule their world. We know the dangers that surround them. They lack the experience and knowledge to make good choices. As an adult, we see the whole picture better than they do.
It is our responsibility to allow them to do what they are equipped to do. We want them to grow and mature but safely. As they grow, they will begin to see the wisdom of their elders, being thankful for the guidance. (Of course, this usually occurs only when they become the parents of children.)
Jesus' disciples, like small children, were trying to get positioned to rule in the Kingdom. They envisioned it to be like the world's kingdoms, requiring men of power to run things.
Jesus taught that the Kingdom already has a King whose rule is perfect, having no need of any advisor. We are called to serve our King and our neighbor. By the mercy and grace that has redeemed us, we do His will in His Kingdom.