Your heart is a throne room, and what you desire most sits on that throne. Whoever, or whatever, sits on the throne of your heart is the king of your life. If your greatest desire is to be happy, then happiness is your king. If it's to be wealthy, then money is your king. If it's to be a good person, then morality is your king. Your deepest desire rules over you.
As you grow older you find that these deep desires are not benevolent monarchs. They are malevolent tyrants. They don't lead you with a gentle hand, they crush your neck under their boot. They infest your soul and dominate your mind. You obsess over these desires until they make you their slave.
But did you know that you are created in the image of God? Of all the things God has ever created, of all the things that exist in the universe, only human beings are made in his image. You are the greatest thing in creation, and nothing less than you has any right to sit on the throne of your heart. That throne belongs to the only one who is greater than you--God himself. Remove the low things from the throne room of your heart, and invite God to take his rightful place as your King.