This is a quote from the book The Existence and Attributes of God, sermons published after his death.
"We make an idol of our own wills, and as much as self is exalted, God is deposed, the more we esteem our own wills, the more we endeavor to annihilate the will of God; account nothing of him, the more we account of ourselves, and endeavor to render ourselves his superiors, by exalting our own wills..... To make ourselves, our own rule, and the object of our chiefest love, is atheism. If self-denial be the greatest part of godliness, the great letter in the alphabet of religion; self-love is the great letter in the alphabet of practical atheism. Self is the great antichrist and the anti-God in the world, that sets up itself above all that is called God; self-love..... sits in the temple of God, and would be adored as God."
The language is a bit old fashioned and the sentences long but I am blown away by the truth of this as I've looked in my own heart to see where I pit my will against God - not in deliberate defiance, but in just choosing to do what I want in a situation without following God's ways.