“If our purpose is to fight the spiritual fight and to defeat, with God’s help, the demons of malice, we should take every care to guard our heart from the demon of dejection, just as a moth devours clothing and a worm devours wood, so dejection devours a man’s soul. It persuades him to shun every helpful encounter and stops him accepting advice from his true friends or giving them a courteous and peaceful reply. Seizing the entire soul, it fills it with bitterness and listlessness. Then it suggests to the soul that we should go away from other people, since they are the cause of its agitation. It does not allow the soul to understand that its sickness does not come from without, but lies hidden within, only manifesting itself when temptations attack the soul because of our ascetic efforts.
A man can be harmed by another only through the causes of the passions which lie within himself. It is for this reason that God, the Creator of all and the Doctor of men’s souls, who alone has accurate knowledge of the soul’s wounds, does not tell us to forsake the company of men; He tells us to root out the causes of evil within us and to recognize that the soul’s health is achieved not by a man’s separating himself from his fellows, but by his living the ascetic life in the company of holy men. When we abandon our brothers for some apparently good reason, we do not eradicate the motives for dejection but merely exchange them, since the sickness which lies hidden within us will show itself again in other circumstances.”
— St. John Cassian