The heaven for height, and the earth for depth, and the heart of kings is unsearchable.
Proverbs 25:3, KJV

There are three ways to understand this verse, I think:

1. Very few throughout all of history can understand the pressures, stresses, and rewards of leading a people as ruler or even elected official. Some of us may get an inkling of some idea, but without doing it we will never have a full understanding. (Consider the presidents and prime ministers who enter office with dark hair that turns gray during one term.)
2. God, the Creator of all of space and the Earth as well as our Eternal King, can never be fully understood. How can finite creatures understand that much power and majesty or that this God would want to save people who willfully rebel against Him? It will never happen.
3. As I mentioned the other day, Christians are are a royal priesthood following our King of kings and High Priest. Unbelievers will try to understand all of space and our Earth, but they may never understand how we can believe in the One who made it all. They will barely if at all attempt to search out our heart for our King.

Most of us will never understand leading a nation, and none of us will ever comprehend the fullness of God.

If we are wise, we will seek out God and contemplate His truths and all He has done for us. We may not understand all He has done, but diving into those unsearchable truths will only bring us closer to and more like that God.