Excerpt from The Life of St. Antony:

And since I have become a fool in detailing these things, receive this also as an aid to your safety and fearlessness; and believe me for I do not lie. Once some one knocked at the door of my cell, and going forth I saw one who seemed of great size and tall. Then when I enquired, "Who art thou?" he said, "I am Satan." Then when I said, "Why art thou here?" he answered, "Why do the monks and all other Christians blame me undeservedly? Why do they curse me hourly?" Then I answered, "Wherefore dost thou trouble them?" He said, "I am not he who troubles them, but they trouble themselves, for I am become weak. Have they not read, "The swords of the enemy have come to an end, and thou hast destroyed the cities ?" I have no longer a place, a weapon, a city. The Christians are spread everywhere, and at length even the desert is filled with monks. Let them take heed to themselves, and let them not curse me unreservedly." Then I marvelled at the grace of the Lord, and said to him: "Thou who art ever a liar and never speakest the truth, this at length, even against thy will, thou hast truly spoken. For the coming of Christ hath made thee weak, and He hath cast thee down and stripped thee." But he having heard the Saviour's name, and not being able to bear the burning from it, vanished.

'If, therefore, the devil himself confesses that his power is gone, we ought utterly to despise both him and his demons; and since the enemy with his hounds has but devices of this sort, we, having got to know their weakness, are able to despise them. Wherefore let us not despond after this fashion, nor let us have a thought of cowardice in our heart, nor frame fears for ourselves, saying, I am afraid lest a demon should come and overthrow me; lest he should lift me up and cast me down; or lest rising against me on a sudden he confound me. Such thoughts let us not have in mind at all, nor let us be sorrowful as though we were perishing; but rather let us be courageous and rejoice always, believing that we are safe Let us consider in our soul that the Lord is with us, who put the evil spirits to flight and broke their power. Let us consider and lay to heart that while the Lord is with us, our foes can do us no hurt. For when they come they approach us in a form corresponding to the state in which they discover us, and adapt their delusions to the condition of mind in which they find us. If, therefore, they find us timid and confused, they forthwith beset the place, like robbers, having found it unguarded; and what we of ourselves are thinking, they do, and more also. For if they find us faint-hearted and cowardly, they mightily increase our terror, by their delusions and threats; and with these the unhappy soul is thenceforth tormented. But if they see us rejoicing in the Lord, contemplating the bliss of the future, mindful of the Lord, deeming all things in His hand, and that no evil spirit has any strength against the Christian, nor any power at all over any one--when they behold the soul fortified with these thoughts--they are discomfited and turned backwards. Thus the enemy, seeing Job fenced round with them, withdrew from him; but finding Judas unguarded, him he took captive. Thus if we are wishful to despise the enemy, let us ever ponder over the things of the Lord, and let the soul ever rejoice in hope. And we shall see the snares of the demon are like smoke, and the evil ones themselves flee rather than pursue For they are, as I said before, exceeding fearful, ever looking forward to the fire prepared for them.