“Abba Poemen said, ‘The will of man is a brass wall between him and God and a stone of stumbling.
When a man renounces it, he is also saying to himself, “By my God, I can leap over the wall.” (Ps. 18.29) If a man’s will is in line with what is right, then he can really labor,’ […] Abraham, the disciple of Abba Agathon, questioned Abba Poemen saying, ‘How do the demons fight against you? They do not fight against us at all as long as we are doing our own will.
For our own wills become the demons, and it is these which attack us in order that we may fulfill them. But if you want to see who the demons really fight against, it is against Moses and those who are like him.’” (Poemen in The Sayings of the Desert Fathers, pp 174, 176)