Pride

Only a humble person can be thankful for everything. He knows he deserves nothing and therefore gives thanks even for the smallest things. Lack of thankfulness comes from pride and thinking you deserve better. Pride tries to convince a man that his job, health, spouse is not as good as he deserves. Pride was the root of the first sin and remains the root of all sin. Satan's pride led him to rebel against God. The pride of Adam and Eve led them to believe Satan's lie that they deserved more than they had, even the right to be as God.