“A man must first recognize and consider what his sin is, and know the plague of his heart before he can be duly humbled for it. Th first creature God made was light. So the first thing in a penitent is illumination: ‘Now ye are light in the Lord’ (Eph. 5:8). The eye is made both seeing and weeping. Sin must first be seen before it can be wept for.
Hence I infer that where there is no sight of sin, there can be no repentance. Many who can spy faults in others see none in themselves. They cry they have good hearts. Is it not strange that two should live together, and eat and drink together, yet not know each other? Such is the case of the sinner. His body and soul live together, work together, yet is unacquainted with himself. He knows not his own heart, nor what a hell he carries about him. Under a veil a deformed face is hid. Persons are veiled over with ignorance and self-love; therefore they see bit what deformed souls they have. The devil does with them as the falconer with the hawk. He blinds them and carries them hooded to hell: ‘the sword shall be upon his right eye’ (Zech. 11:17).
– Thomas Watson. The Doctrine of Repentance, p. 18-19