Resentment and gratitude cannot coexist, since resentment blocks the perception and experience of life as a gift. My resentment tells me that I don’t receive what I deserve. It always manifests itself in envy. The discipline of gratitude is the explicit effort to acknowledge that all I am and have is given to me as a gift of love, a gift to be celebrated with joy. Gratitude as a discipline involves a conscious choice. I can choose to be grateful even when my emotions and feelings are still steeped in hurt and resentment. I can choose to be grateful when I am criticized, even when my heart still responds in bitterness. There is always the choice between resentment and gratitude.
― Henri J.M. Nouwen, The Return of the Prodigal Son: A Story of Homecoming