In other words, gratitude flourishes in the sphere of grace. And that is why the play on words in 2 Corinthians 4:15 is significant. Grace is charis and gratitude is eucharistian because gratitude is a response to grace. Gratitude is the feeling of happiness you feel toward somebody who has shown you some undeserved kindness, that is, who has been gracious to you.
John Piper
Website: http://www.desiringgod.org/messages/grace-gratitude-and-the-glory-of-god