What is gratitude? It’s more than only saying, “thank you” for blessings received, as John Piper explains:
…gratitude that is pleasing to God is not first a delight in the benefits God gives (though that will be part of it). True gratitude must be rooted in something else that comes firstnamely, a delight in the beauty and excellency of God’s character. If this is not the foundation of our gratitude, then it is not above what the “natural man,” apart from the Spirit and the new nature in Christ, experiences. In that case “gratitude” to God is no more pleasing to God than all the other emotions that unbelievers have without delighting in him.
You would not be honored if I thanked you often for your gifts to me but had no deep and spontaneous regard for you as a person. You would feel insulted, no matter how much I thanked you for your gifts. If your character and personality do not attract me or give me joy in being around you, then you will just feel used, like a tool or a machine to produce the things I really love.
So it is with God. If we are not captured by his personality and character, displayed in his saving work, then all our declarations of thanksgiving are like the gratitude of a wife to a husband for the money she gets from him to use in her affair with another man. [John Piper, God is the Gospel, 136-7.]