Abba Peter, the disciple of Abba Lot, said, One day when I was in Abba Agathon’s cell a brother came in and said to him, “I want to live with the brethren; tell me how to dwell with them.” The old man answered him, “All the days of your life keep the frame of mind of the stranger which you have on the first day you join them, so as not to become too familiar with them.” The Abba Macarius asked, “And what does this familiarity produce?” the old man replied, “It is like a strong, burning wind, each time it arises everything flies swept before it, and it destroys the fruit of the trees.” So Abba Macarius said, “Is speaking too freely really as bad as all that?” Abba Agathon said, “No passion is as worse than an uncontrolled tongue, because it is the mother of all the passions.” Accordingly the good workman should not use it, even as he is living as a solitary in the cell. I know a brother who spent a long time in his cell using a small bed who said, “I should have left my cell without making use of that small bed if no one had told me it was there.” It is the hard-working Monk who is a warrior.
The brethren also asked Abba Agathon “Amongst all good works, which is the virtue which requires the greatest effort?” He answered “Forgive me, but I think there is no labor greater than that of prayer to God. For every time a man wants to pray, his enemies, the demons, want to prevent him. For they know that it is only by turning him from prayer that they can hinder his journey. What ever good work a man undertakes, if he perseveres in it, he will attain rest. But prayer is warfare to the last breath.
The same Abba said “a man who is angry, even if he were to raise the dead, is not acceptable to God”