Every animal has within itself certain instincts which it has received from God, for the preservation of its own being. Wherefore Christ has also given us this warning, that what comes to them by nature, may be ours by the aid of reason and prudence: that we may flee from sin as the brute creatures shun deadly food, but that we seek after righteousness, as they wholesome herbs. Therefore saith He, Take heed to yourselves, that is, that you may distinguish the noxious from the wholesome. But since there are two ways of taking heed to ourselves, the one with the bodily eyes, the other by the faculties of the soul, and the bodily eye does not reach to virtue; it remains that we speak of the operations of the soul. Take heed, that is, Look around you on all sides, keeping an ever watchful eye to the guardianship of your soul. He says not, Take heed to your own or to the things around, but to yourselves. For ye are mind and spirit, your body is only of sense. Around you are riches, arts, and all the appendages of life, you must not mind these, but your soul, of which you must take especial care. The same admonition tends both to the healing of the sick, and the perfecting of those that are well, namely, such as are the guardians of the present, the providers of the future, not judging the actions of others, but strictly searching their own, not suffering the mind to be the slave of their passions, but subduing the irrational part of the soul to the rational. But the reason why we should take heed He adds as follows, Lest at any time your hearts be overcharged, &c.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Hom. 1. in illud Atten de tibi.