Observe your thoughts, and beware of what you have in your heart and your spirit, knowing that the demons put ideas into you so as to corrupt your soul by making it think of that which is not right, in order to turn your spirit from the consideration of your sins and of God.
Charity, temperance, contemplation, and prayer please God; gluttony, licentiousness, and what multiplies them, please the flesh. Therefore they who are in the flesh cannot please God. And they that are Christ’s have crucified their flesh with the passions and concupiscences.
When an archer desires to shoot his arrows successfully, he first takes great pains over his posture and aligns himself accurately with his mark. It should be the same for you who are about to shoot the head of the wicked devil. Let us be concerned first for the good order of sensations and then for the good posture of inner thoughts.
As a man cannot remain unscathed who spares his enemy on the field of battle, so a man engaged in spiritual warfare cannot save his soul if he spares his body.
Understand me. It is so simple. People who do not know God, or who go against Him, are to be pitied; the heart sorrows for them and the eye weeps. Both paradise and torment are clearly visible to us: We know this through the Holy Spirit. And did not the Lord Himself say, 'The kingdom of God is within you?' Thus eternal life has its beginning here in this life; and it is here that we sow the seeds of eternal torment.
When your brother is disturbed and reacts to what you say to him, control your tongue lest you speak even one word in wrath and do not allow yourself to be arrogant concerning him in your heart but remember that he is your brother, a member of Christ and an image of God, influenced by the common enemy. Be merciful and show pity on him because it is possible that the devil through your wrath, will capture his soul and mortify it in resentment and thus, through your carelessness, the soul for whom Christ died is lost (1 Cor. 5:11).
Having guarded ourselves against distractions and worries, let us turn our attention to our body on which mental vigilance is completely dependent. Human bodies differ widely from one another in strength and health. Some by their strength are like copper and iron; others are frail like grass. For this reason everyone should rule his body with great prudence, after exploring his physical powers. For a strong and healthy body, special fasts and vigils are suitable; they make it lighter, and give the mind a special wakefulness. A weak body should be strengthened by food and sleep according to one's physical needs, but on no account to satiety. Satiety is extremely harmful even for a weak body; it weakens it, and makes it susceptible to disease. Wise temperance of the stomach is a door to all the virtues. Restrain the stomach, and you will enter Paradise. But if you please and pamper your stomach, you will hurl yourself over the precipice of bodily impurity, into the fire of wrath and fury, you will coarsen and darken your mind, and in this way you will ruin your powers of attention and self-control, your sobriety and vigilance…
When you intend to do something and see that your thought is perturbed, and if after invoking God's Name it remains perturbed even by a hair's breadth, know from this that the action you mean to commit is from the evil one and refrain from commiting it. For nothing done with perturbation is pleasing to God.
Let us avail ourselves of the example of that holy staretz who used to say: 'Depart, evil one; come, beloved!' Once a brother who overheard his words and supposed that the staretz was speaking to another man asked him 'With whom are you conversing, father?' And the staretz answered: 'I am driving away evil thoughts and calling the good ones to my side.' And so, if we are tempted, let us use the words of that staretz, or others like them.