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.
The man of Christ embarks upon the path of divine perfection by overcoming, with the aid of evangelical virtues, the sin and evil within him and in the world around him. He constantly marches on from one good to another, from smaller to greater, from greater to greatest. In this progress he never pauses, for any delay would bring spiritual stagnation, numbness, death. Through every pure thought, every holy sentiment, every good desire and kindly word, he progresses toward resurrection, immortality, eternal life.
If a man has some spiritual gift and feels compassion for those who do not have it, he preserves the gift because of his compassion. But a boastful man will lose it through succumbing to the temptations of boastfulness.
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).
There is no venom more poisonous than that of the asp or cobra, and there is no evil greater than that of self-love. The winged children of self-love are self-praise, self-satisfaction, gluttony, unchastity, self-esteem, jealousy and the crown of all these, pride. Pride can drag down not men alone, but even angels from heaven, and surround them with darkness instead of light.
Watchfulness and the Jesus Prayer, as I have said, mutually reinforce each other, for close attentiveness goes with constant prayer, while prayer goes with close watchfulness and attentiveness of intellect.
The hour of death will come upon us, it will come, and we shall not escape it. May the prince of this world and of the air (cf. John 14:30; Eph. 2:2) find our misdeeds few and petty when he comes, so that he will not have good grounds for convicting us. Otherwise we shall weep in vain. 'For that servant who knew his lord's will and did not do it as a servant, shall be beaten with many stripes' (cf. Luke 12:47).
Fear God and keep His commandments both in your feelings and in your intellect. If you force yourself to keep them in your intellect, bit by bit you will attain to fulfilling them in your feelings.
In Christianity truth is not a philosophical concept nor is it a theory, a teaching, or a system, but rather, it is the living theanthropic hypostasis - the historical Jesus Christ (John 14:6). Before Christ men could only conjecture about the Truth since they did not possess it. With Christ as the incarnate divine Logos the eternally complete divine Truth enters into the world. For this reason the Gospel says: 'Truth came by Jesus Christ' (John 1:17).
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.
Continuity of attention produces inner stability; inner stability produces a natural intensification of watchfulness; and this intensification gradually and in due measure gives contemplative insight into spiritual warfare. This in its turn is succeeded by persistence in the Jesus Prayer and by the state that Jesus confers, in which the intellect, free from all images, enjoys complete quietude.
Bring before your eyes the blessings, whether physical or spiritual, conferred on you from the beginning of your life down to the present, and call them repeatedly to mind in accordance with the words: 'Forget not all His benefits' (Ps. 102:2). Then your heart will readily be moved to the fear and love of God, so that you repay Him, as far as you can. by your strict life, virtuous conduct, devout conscience, wise speech, true faith and humility - in short, by dedicating your whole self to God. When you are moved by the recollection of all these blessings which you have received through God's loving goodness, your heart will be spontaneously wounded with longing and love through this recollection or, rather, with the help of divine grace.