Prayer and fasting, worship and adoration, Scripture and sacraments and sacramentals all provide the weapons of our spiritual warfare. With them we go on the offensive against the Evil One. But the virtues provide our defense armor. As Blessed Pope Paul VI once observed, St. Paul ‘used the armor of a soldier as a symbol for the virtues that can make a Christian invulnerable.’ They are our best defense against his attacks, for they guard our minds and hearts from his deceptions and temptations. A lapse in virtue is in fact a chink in our armor that makes us vulnerable.
Manual for Spiritual Warfare, p. 57-8