Even when your body does nothing, sin can be active in your mind. When your soul inwardly repulses the evil one's attack by means of prayer, attention, remembrance of death, godly sorrow and mourning the body, too, takes its share of holiness, having acquired freedom from evil actions. This is what the Lord meant by saying that someone who cleans the outside of the cup has not cleansed it inside, but clean the inside and the whole cup will be clean (cf. Mt. 23:25-26).
St. Gregory Palamas