“The light of true knowledge makes it possible to discern without error the difference between good and evil. Then the path of justice, which leads to the Sun of Justice, brings the mind into the limitless light of knowledge, since it never fails to seek the love of God with all confidence.
Therefore, we must maintain great stillness of mind, even in the midst of our struggles. We shall then be able to distinguish between the different types of thoughts that come to us: those that are good, those sent by God, we will treasure in our memory; those that are evil and inspired by the devil we will reject. A comparison with the sea may help us. A tranquil sea allows the fisherman to gaze right to its depths. No fish can hide there and escape his sight. The stormy sea, however, becomes murky when it is agitated by the winds. The very depths that it revealed in its placidness, the sea now hides. The skills of the fisherman are useless.
Only the Holy Spirit can purify the mind: unless the strong man enters and robs the thief, the booty will not be recovered. So by every means, but especially by peace of soul, we must try to provide the Holy Spirit with a resting place...”~Diadochus of Photice