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.
It is always possible to make a new start by means of repentance. 'You fell,' it is written, 'now arise'(cf. Prov. 24:16). And if you fall again, then rise again, without despairing at all of your salvation, no matter what happens. So long as you do not surrender yourself willingly to the enemy, your patient endurance, combined with self-reproach, will suffice for your salvation. 'For at one time we ourselves went astray in our folly and disobedience,' says St. Paul. '... Yet He saved us, not because of any good things we had done, but in His mercy' (Tit. 3:3,5).
No Christian believing rightly in God should ever be off his guard. He should always be on the look-out for temptation, so that when it comes he will not be surprised or disturbed, but will gladly endure the toil and affliction it causes, and so will understand what he is saying when he chants with the prophet: 'Prove me, O Lord, and try me' (Ps. 26:2 LXX). For the prophet did not say, 'Thy correction has destroyed me,' but, 'it has upheld me to the end' (Ps. 18:35 LXX).
Not every man can be trusted when giving advice to those who seek it. We can trust only him who has received from God the grace of discrimination and who ... has acquired through great humility and long practice of the virtues an intellect blessed with spiritual insight. Such a man is in a position to advise, not everyone, but at least those who seek him out voluntarily and who question him by their own choice; for he has learned things in their true order.
One time St. Nicodemos, on a feast day, was walking toward the Great Lavra (on Mt Athos). On his way he came across a kellion where he spent the night. At midnight he saw an elder and his accompanying monks entering the church. He secretly went in also, and there he saw the elder and his subordinate monks uttering the Jesus Prayer ('Lord Jesus Christ, Son of God, have mercy on me'), sometimes in a kneeling position, sometimes standing up. And at the time of the Holy Communion, he saw all their faces shining only a little less dimly than the sun.
If we desire to acquire faith the foundation of all blessings, the door to God's mysteries, unflagging defeat of our enemies, the most necessary of all the virtues, the wings of prayer and the dwelling of God within the soul--we must endure every trial imposed by our enemies and by our many and various thoughts... if we forcibly triumph over the trials and temptations that befall us, it will not be we who are victorious, but Christ, Who is present in us through faith.
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).
It is not always possible to fulfill the usual rules; one must take circumstances into account and try to fulfill what they make possible, as far as one can. The demons themselves are not unmindful of this law. So, being in constant enmity with us, they prevent us from doing what is possible and urge us to do what is impossible.
If anyone thinks that he has love but does not have the same love for all, but distinguishes between persons, separating the lowly from the rich, the infirm from the healthy, a sinner from a righteous man, one far off from one near, one who is an enemy from one who loves you, such love is not perfect, but partial. Actual and perfect love consists in considering everyone and loving them equally, both those who love you and those who hate you. Such love, with which mercy is inseparable, is, in brief, a net for all virtues. It embraces and contains all the commandments of God within itself.
