Entitlement is the only sin.
"Value the least gifts no less than the greatest, and simple graces as especial favours. If you remember the dignity of the Giver, no gift will seem small or mean, for nothing can be valueless that is given by the most high God." Thomas A Kempis
Entitlement has many names, for it is legion. Pride, self-will, esteem of self, hubris, audacity, call it what you will. Its core is a sense that whatever I have is not good enough; or worse, the good things I have are good enough, and I deserve them. The universe, God, whatever, owes it to me. "I'm grateful because it's what I deserve" is just as bad as "I'm ungrateful because it's not what I deserve."
When Adam and Eve plucked the fruit of the garden, what was their sin? Disobedience, surely. Gluttony, surely. Impatience, believing a serpent rather than God, yes yes. I think the core was a feeling of entitlement that overcame their love for God. "This fruit is good, and I deserve it. It belongs to me." They were right; it was good. But they were wrong -- we should get no good thing until God decides... and even then we should be overcome with how unworthy and grateful we are!
What we deserve is exactly and precisely nothing, nil, nada. So the appropriate affection springing from awareness of any fact is gratitude, joy, and thanks. Awareness of being rather than non-being, of life rather than mere mineral existence, of rationality rather than mere sentience, of self-awareness rather than stupidity, of freedom of choice rather than machine-like auto-motion, of the curse of physical death rather than everlasting slavery to sin, of forgiveness rather than wrath, of clear communication of his word rather than forsaking us in our transgressions, of showing us how to obey rather than just telling us, of the gift of divinity rather than the curse of bestiality of blessings rather than curses -- the correct affection in every case is absolute, unqualified and life-shattering gratitude. Even awareness of God's wrath is cause for gratitude, for he gives us his divine wrath rather than divine apathy. I would rather go to hell because God hates my sin than to lie on earth because God does not even care that I am sick.
A Kempis again says, " Even if awards punishment and pain, accept them gladly, for whatever he allows to befall us is always for our salvation."