Sin is what you do when your heart is not satisfied with God. No one sins out of duty. We sin because it holds out some promise of happiness. That promise enslaves us until we believe that God is more to be desired than life itself (Psalm 63:3). Which means that the power of sin's promise is broken by the power of God's.
John PiperIf we have no zeal for the glory of God our mercy must be superficial, man-centred human improvement with no eternal significance. And if our zeal for the glory of God is not a revelling in his mercy, than our so-called zeal, in spite of all its protests, is our of touch with God and hypocritical.
John Piper