Charles H. Spurgeon on Psalms 19:12

"Secret faults." "Secret sins" are more dangerous to the person in some respects than open sins. For a man doth, by his art of sinning, deprive himself of the help of his sinfulness. Like him who will carry his wound covered, or who bleeds inwardly, help comes not in because the danger is not descried or known. If a man's sin breaks out there is a minister at hand, a friend near, and others to reprove, to warn, to direct; but when he is the artificer of his lusts, he bars himself of all public remedy, and takes great order and care to damn his soul, by covering his "secret sins" with some plausible varnish which may beget a good opinion in others of his ways. A man does by his secrecy give the reins unto corruption: the mind is fed all the day long either with sinful contemplations or projectings, so that the very strength of the soul is wasted and corrupted. Nay, secret actings do but heat and inflame natural corruption. As in shouldering in a crowd, when one hath got out of the door, two or three are ready to fall out after; so when a man hath given his heart leave to act a secret sin, this begets a present, and quick, and strong flame in corruption to repeat and multiply and throng out the acts. Sinful acts are not only fruits of sin, but helps and strengths, all sinning being more sinful by more sinning, not only in the effects but in the cause: the spring and cause of sin will grow mad and insolent hereby, and more corrupt; this being a truth, that if the heart gives way for one sin, it will be ready for the next; if it will yield to bring forth once at the devil's pleasure, it will bring forth twice by its own motion. A man by "secret sins" doth but polish and square the hypocrisy of his heart: he doth strive to be an exact hypocrite; and the more cunning he is in the palliating of his sinnings, the more perfect he is in his hypocrisy. —Obadiah Sedgwick.