But when the Holy Spirit dwells in the heart of a person, He shows him all his inner poverty and weakness, and the corruption of his heart and soul, and his separation from God; and with all his virtues and righteousness. He shows him his sins, his sloth and indifference regarding the salvation and good of people, his self-seeking in his apparently most disinterested virtues, his coarse selfishness even where he does not suspect it. To be brief, the Holy Spirit shows him everything as it really is. Then a person begins to have true humility, begins to lose hope in his own powers and virtues, regards himself as the worst of men.
And when a person humbles himself before Jesus Christ Who alone is Holy in the glory of God the Father, he begins to repent truly, and resolves never again to sin but to live more carefully. And if he really has some virtues, then he sees clearly that he practiced and practices them only with the help of God, and therefore he begins to put his trust only in God.
~ St. Innocent of Irkutsk, Indication of the Way Into the Kingdom of Heaven