To act 'according to one’s strength' means to use a little less than necessary both of food, and drink, and sleep... As for food, restrain yourself when you wish to eat a little more, and in this way you will always make use of it moderately.
Leave off all evasions, bend your neck to humility and obedience, and you will receive mercy. If you practice with humility and obedience what you hear from the fathers, God will grant you His blessed help not only in the work you are doing, but will make all your works successful, for He protects the path of those who fear Him and watches their progress.
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.
But a sober and prudent man who desires to be saved, when he sees from what it is that he suffers harm, carefully preserves himself from evil remembrances, is not drawn into passionate thoughts, avoids meetings and conversations with those for whom he feels attraction and avoids every occasion for sin, fearing lest he himself ignite a fire within himself. This is the warfare which proceeds from one’s own lust, which a man brings on himself
Silence of lips is better and more wonderful than any edifying conversation. Strive to acquire humility and submissiveness. Never insist that anything should be according to your will, for this gives birth to anger. Do not judge or humiliate anyone, for this gives birth to anger. Do not judge or humiliate anyone, for this exhausts the heart and blinds the mind, and thereon leads to negligence and makes the heart unfeeling.
If the Lord delays granting you full victory over your enemies and puts it off to the last day of your life, you must know that He does this for your own good; so long as you do not retreat or cease to struggle wholeheartedly. Even if you are wounded in battle, do not lay down your arms and turn to flight. Keep only one thing in your mind and intention - to fight with all courage and ardor, since it is unavoidable. No man can escape this warfare, either in life or in death. And he who does not fight to overcome his passions and his enemies will inevitably be taken prisoner, either here or yonder, and delivered to death.
After a man has decided to abandon his wrong ways and actually does abandon them, the first task of the enemy is to clear a space for an unhampered field of action against him. He succeeds in this by suggesting to a man, who has entered the right path, that he should act on his own, and not go for advice and guidance to the teachers of righteous life, who are always attached to the Church. A man who follows their guidance and verifies all his actions, both inner and outer, by the good judgement of his teachers - priests in their parishes in the case of laymen, experienced startzi in monasteries - cannot be approached by the enemy. Whatever he may suggest, the experienced eye will at once see where he is driving and will warn his pupil. In this way all his wiles are defeated. But if a man turns away from his teachers, the enemy will at once confuse him and lead him astray ... There are many possibilities, which do not look evil; and those he suggests... the novice, who, feeling thus free and unhampered, begins to imagine that this good state is the fruit of his own efforts, and so rests in them.
The incessant invocation of God's name is a medicine which mortifies not just the passions, but even their influence. Just as the physician puts medications or dressings on a wound that it might be healed, without the patient even knowing the manner of their operation, so also the name of God, when we invoke it, mortifies all passions, though we do not know how that happens.
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.
Give thanks to God for all things, because thanksgiving is intercession before God for our weakness. Judge yourself always and in everything as a sinner and as one seduced - and so God will not judge you; be humble in everything and you will receive grace.
Concerning fasting, do not grieve, as I have said to you before: God does not demand of anyone labors beyond his strength. And indeed, what is fasting if not a punishment of the body in order to humble a healthy body and make it infirm for passions, according to the word of the Apostle: 'When I am weak, then am I strong' (II Corinthians 12:10).
If the Lord delays granting you full victory over your enemies and puts it off to the last day of your life, you must know that He does this for your own good; so long as you do not retreat or cease to struggle wholeheartedly. Even if you are wounded in battle, do not lay down your arms and turn to flight. Keep only one thing in your mind and intention - to fight with all courage and ardor, since it is unavoidable. No man can escape this warfare, either in life or in death. And he who does not fight to overcome his passions and his enemies will inevitably be taken prisoner, either here or yonder, and delivered to death.
Never allow yourself boldly to judge your neighbor; judge and condemn no one, ... rather have compassion and pity for him, but let his example be a lesson in humility to you; realizing that you too are extremely weak and as easily moved to sin as dust on the road, say to yourself: 'He fell today, but tomorrow I shall fall.'
Do not judge and do not belittle anyone, because from this the heart grows faint and the mind is blinded, and from this, negligence appears and unfeelingness of heart is born. Keep ceaseless vigil, learning in the law of God, for through this the heart is warmed by heavenly fire, as is said: 'In my meditation a fire was kindled.'