Chapter IV. Whence and in what way dejection arises.
Works of St John Cassian (Institutes, Conferences, On the Incarnation) · Saint John Cassian
But sometimes it is found to result from the fault of previous anger, or to spring from the desire of some gain which has not been realized, when a man has found that he has failed in his hope of securing those things which he had planned. But sometimes without any apparent reason for our being driven to fall into this misfortune, we are by the instigation of our crafty enemy suddenly depressed with so great a gloom that we cannot receive with ordinary civility the visits of those who are near and dear to us; and whatever subject of conversation is started by them, we regard it as ill-timed and out of place; and we can give them no civil answer, as the gall of bitterness is in possession of every corner of our heart.
Cassian 1.183.2