Thankfulness is the joyful and humble response of a heart that has been transformed by grace…Thankfulness is a good test of your faith. Its absence demonstrates that your faith is more lip service than experiential knowledge…  ~Joe Thorn

Ann Voskamp makes a similar point in One Thousand Gifts: If I’m ruthlessly honest, I may have said yes to God, yes to Christianity, but really, I have lived the no.
I have lived the no, too. I think I’m daily tempted to live the no. No, God, I don’t accept Your will. No, God, I’m not going to do it your way. No, God, I refuse to move until I understand. Unless I agree. Until I know. Unless I can see. I believe, but I don’t. I’m grateful, but I’m not.
I want to be filled with thankfulness. Flowing in genuine gratitude. Not lip service thankfulness, but the kind that comes from an intimate knowledge of His grace. Seeing His goodness in everything. Trusting Him at all times. Being content in all things.  
Lord, forgive me for my lip service thanks. And forgive me for my ingratitude. For giving myself over to thoughts of what’s missing rather than meditating on all that You’ve given. Transform me by Your grace. And change forever the way I see things. Change my perspective, that I would be absolutely convinced, with a child-like enchantment, of Your goodness, Your presence, Your love, and Your delight in me.