Our incensive power is also a good defense against this demon [of unchastity]. When it is directed against evil thoughts of this kind, such power fills the demon with fear and destroys his designs. And this is the meaning of the statement: ‘Be angry, and do not sin’ (Ps. 4:4). Such anger is a useful medicine for the soul at times of temptation.
As sheep to a good shepherd, the Lord has given to man intellections (“logismoi”) of this present world; for it is written: ‘He has given intellect to the heart of every man’ (cf. Heb. 10:16). To help man, He has given him incensive power and desire, so that with the first he may drive away wolflike intellections, while with the second he may lovingly tend the sheep, even though he is often exposed to rains and winds. In addition, God has given man the law, so that he may shepherd the sheep; He has given him green pastures and refreshing water (cf. Ps. 23:2), a psaltery and harp, a rod and staff. In this way, he gathers hay from the mountains and is fed and clothed from his flock; for it is written, ‘Does anyone feed a flock and not drink its milk?’ (1 Cor. 9:7). Therefore, the solitary ought to guard this flock night and day, making sure that none of the lambs is caught by wild beasts or falls into the hands of thieves. Should this happen in some valley, he must at once snatch the creature from the mouth of the lion or the bear (cf. 1 Sam. 17:35).
What does it mean for the lambs to be caught by wild beasts? It means that when we think about our brother we feed on hatred; when we think about a woman we are moved with shameful lust; when we think about gold and silver we are filled with greed; and likewise when we think about gifts received from God, our mind is gorged with self-esteem. The same happens in the case of other intellections if they are seized by the passions. We must not only guard this flock by day, but also keep watch at night; for by having fantasies of shameful and evil things we may lose some of the sheep entrusted to us.