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.
Even a pious person is not immune to spiritual sickness if he does not have a wise guide -- either a living person or a spiritual writer. This sickness is called prelest, or spiritual delusion, imagining oneself to be near to God and to the realm of the divine and supernatural. Even zealous ascetics in monasteries are sometimes subject to this delusion, but of course, laymen who are zealous in external struggles (podvigi) undergo it much more frequently. Surpassing their acquaintances in struggles of prayer and fasting, they imagine that they are seers of divine visions, or at least of dreams inspired by grace. In every event of their lives, they see special intentional directions from God or their guardian angel. And then they start imagining that they are God's elect, and often try to foretell the future. The Holy Fathers armed themselves against nothing so fiercely as against this sickness -- prelest.
When tested by some trial you should try to find out not why or through whom it came, but only how to endure it gratefully, without distress or rancor.
Acquire humility, which scorches the demons, obedience, which opens the door for the Son of God to enter a man, faith which saves a man, hope which makes him unashamed; and love which lets not a man fall away from God.
He who wants to cross the spiritual sea is long-suffering, humble, vigilant and self-controlled. If he impetuously embarks on it without these four virtues, he agitates his heart, but cannot cross.
The mission of the Church is to bring about in her members the conviction that the proper state of human personhood is composed of immortality and eternity and not of the realm of time and mortality... and the conviction that man is a wayfarer who is wending his way in the sway of time and mortality towards immortality and all eternity.
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.
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.
We then commemorate also those who have fallen asleep before us, first, patriarchs, prophets, apostles, martyrs, that God, by their prayers and intercessions, may receive our petitions.
The Lord commands all men to repent (Matt. 4:17), so that even the spiritual and those making progress should not neglect this injunction and fail to give attention to the smallest and most subtle errors.