The poison of anger…

We must, with God’s help, eradicate the deadly poison of the demon of anger from the depths of our souls. So long as he dwells in our hearts and blinds the eyes of the heart with his somber disorders, we can neither discriminate what is for our good, nor achieve spiritual knowledge, nor fulfill our good intentions, nor participate in true life; and our intellect will remain impervious to the contemplation of the true, divine light; for it is written, “Man’s anger does not bring about the righteousness of God” (Jms. 1:20).
— Saint John Cassian (c. 360-435)