Gratitude

Gratitude will always degenerate into the debtor's ethic if it only looks back on past grace and not forward as well to future grace. We honor the nature and aim of God's goodwill by trusting Him to work for us from now on, which means that gratitude functions well as a motive only as it gives rise to faith. Gratitude says to faith, "Keep trusing your Father for more grace; I know He will supply. I have experienced it, and it was sweet." Gratitude does help motivate the radical obedience of love, but it does so indirectly through the service of faith in future grace.

John Piper, Brothers, We Are Not Professionals, pg. 38