The heart is a desire factory. The human heart produces desires as fire produces heat. As surely as sparks fly upward, the heart pumps out desire after desire for a happier future. The condition of the heart is appraised by the kinds of desires that hold sway. Or, to put it another way, the state of the heart is shown by the things that satisfy its desires. If it is satisfied with mean and ugly things, it is a mean and ugly heart. If it is satisfied with God, it is a godly heart.
John Piper, Future Grace, (Multnomah, 1995), 277– 278.