What is the role of grace in our striving?

St. Augustine says, “This, therefore, is now going on for as long as this mortal life of ours subject to grace endures, lest sin, that is, the concupiscence of sin (for in this place he calls this by the name of sin) reign in our mortal body. That is shown to reign, however, when its desires are obeyed. There is, then, a concupiscence of sin within us which must not be permitted to reign; there are its desires which must not be obeyed, or it will reign over those who obey them. Therefore, let not concupiscence usurp for itself our members, but let continence claim them for itself that they might be the instruments of the justice of God, and that they might not be instruments of iniquity unto sin; for, thus sin will not have dominion over us. We are not under the law, which indeed commands the good but does not grant it, but we are under grace, which in making us love what the Law commands can command us as free agents.”⁸¹⁶