Calvin on our self-deception

"It is certain that man never achieves a clear knowledge of himself unless he has first looked upon God's face, and then descends from contemplating him to scrutinise himself. For we always seem to ourselves righteous and upright and wise and holy - this pride is innate in all of us - unless by clear proofs we stand convinced of our own unrighteousness, foulness, folly and impurity. 

"...and because nothing appears within or around us that has not been contaminated by great immorality, what is a little less vile pleases us a thing most pure - so long as we confine our minds within the limits of human corruption. Just so, an eye to which nothing is shown but black objects judges something dirty white or even rather darkly mottled to be whiteness itself.

"...as long as we do not look beyond the earth, being quite content with our own righteousness, wisdom, and virtue, we flatter ourselves most sweetly, and fancy ourselves all but demigods. Suppose we but once begin to raise our thoughts to God, and to ponder his nature and how completely perfect are his righteousness, wisdom, and power - the straightedge to which we must be shaped. Then, what masquerading earlier as righteousness was pleasing in us will soon grow filthy in its consummate wickedness. What wonderfully impressed us under the name of wisdom will stink in its very foolishness."

Calvin's Institutes, Book 1, The Knowledge of God the Creator