42 Wherefore let this be the first thought for the putting on of humility, that God's virgin think not that it is of herself that she is such, and not rather that this best “gift comes down from above from the Father of Lights, with Whom is no change nor shadow of motion.” For thus she will not think that little has been forgiven her, so as for her to love little, and, being ignorant of the righteousness of God, and wishing to establish her own, not to be made subject to the righteousness of God.
In which fault was that Simon who was surpassed by the woman, unto whom many sins were forgiven, because she loved much. But she will have more cautious and true thoughts, that we are so to account all sins as though forgiven, from which God keeps us that we commit them not. Witnesses are those expressions of pious prayers in holy Scriptures, whereby it is shown, that those very things, which are commanded by God, are not done save by His Gift and help, Who commands. For there is a falsehood in the asking for them, if we could do them without the help of His grace.
What is there so generally and chiefly charged, as obedience whereby the Commandments of God are kept? And yet we find this wished for. “You,” says he, “hast charged, that Your commandments be greatly kept.” Then it follows, “O that my ways were directed to keep Your righteousnesses: then shall I not be confounded, while I look unto all Your commandments.” That which he had set down above that God had commanded, that he wished might of himself be fulfilled. This is done assuredly, that there be not sin; but, if there has been sin, the command is that one repent; lest by defense and excuse of sin he perish through pride, who has done it, while he is unwilling that what he has done perish through repentance.
This also is asked of God, so that it may be understood that it is not done, save by His grant from Whom it is asked. “Set,” says he, “O Lord, a watch to my mouth, and a door of continence around my lips: let not my heart turn away unto evil words, to make excuses in sins, with men that work unrighteousness.” If, therefore, both obedience, whereby we keep His commandments, and repentance whereby we excuse not our sins, are wished for and asked, it is plain that, when it is done, it is by His gift that it is possessed, by His help that it is fulfilled, yet more openly is it said by reason of obedience, “By the Lord the steps of a man are directed, and He shall will His way:” and of repentance the Apostle says, “if haply God may grant unto them repentance.”
Source: On Holy Virginity (New Advent)