"...while the Lord is with us, our foes can do us no hurt. "

"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 immediately 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."

From the book

Life of St. Anthony by Saint Athanasius