What is the essence of sin? Playing God; and, as a means to this, refusing to allow the Creator to be God so far as you are concerned. Living, not for Him, but for yourself; loving serving and pleasing yourself without reference to the Creator; trying to be as far as possible independent of Him, taking yourself out of His hands, holding Him at arm’s length, keeping the reins of life in your own hands; acting as if you, and your pleasure, were the end to which all things else, God included, must be made to function as a means – that is the attitude to which sin essentially consists. Sin is exalting oneself against the Creator, withholding the homage due Him, and putting oneself in His place as the ultimate standard of reference in all life’s decisions.
– J.I. Packer from his book entitled God’s Word