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.
You have no peace from thoughts, which impel you to trouble others, and in turn to be troubled by others. But know, my brother, that if we offend by word or deed, we are thereby ourselves offended a hundredfold. Be longsuffering in all things and refrain from letting your own will enter into anything. Carefully examine your thoughts lest they infect your heart with deadly poison (ill temper) and make you take a gnat for a camel, a pebble for a cliff, and lest you become like a man who has a beam in his own eye but beholds the mote in the eye of another.
Do not be despondent when fighting against the incorporeal enemy, but even in the midst of your afflictions and oppression praise the Lord, Who has found you worthy to suffer for Him, by struggling against the subtlety of the serpent, and to be wounded for Him at every hour; for had you not lived piously, and endeavored to become united to God, the enemy would not have attacked and tormented you.
Love does not reflect. Love is simple. Love never mistakes. Likewise believe and trust without refection, for faith and trust are also simple; or better: God, in Whom we believe and in Whom we trust, is an incomplex Being, as He is also simply love.
After careful clearing, we need to sow the good seed so that it may produce good fruit. The person who wants to sow his, field must also hide the seed, dipping it into the earth as otherwise the birds will come and take it, and it will be lost. After that, he awaits the mercy of God until He sends rain and the seed grows. Even if the farmer works hard, clearing, preparing and sowing, if God does not give rain for the seeds, his entire labor is in vain. We also need the same. Even if we on one occasion do something good, we must cover it with humility and show to God our weakness, asking Him to bless our labor since otherwise it is in vain.
If you wish that God should speedily give you hearty faith in prayer, strive with all your heart to speak and to do everything in regard to other people sincerely, and never be deceitful in your dealings with them. If you are straightforward and truthful with others, then God will give you straightforwardness and sincere faith also in reference to Himself.
When you are praying alone, and your spirit is dejected, and you are wearied and oppressed by your loneliness, remember then, as always, that God the Trinity looks upon you with eyes brighter than the sun; also all the angels, your own Guardian Angel, and all the Saints of God. Truly they do; for they are all one in God, and where God is, there are they also. Where the sun is, thither also are directed all its rays. Try to understand what this means.
Your enemy, the evil one, the father of lies, does not slumber; and endeavors, by every means open to him, to harden your heart --- to make it false and crafty, to drive out from it faith and hope in God - together with love for Him and love and sympathy for your neighbor - and to occupy you with worldly, temporal interests. Watch yourself, watch the thoughts of your heart, and do not bind yourself in the chains of worldly desires and pleasures. Let your happiness be in the one God and the human soul.
In order not to be in daily bondage to the passions and the devil, you must set yourself an object to aim at, have this object constantly in view, and endeavor to attain it, conquering all obstacles by the name of the Lord. What is this object? The Kingdom of God, the Divine palace of glory, prepared for believers from the creation of the world. But as this object can only be attained by certain means, it also is necessary to have such means at one's disposal. And what are these means? Faith, hope, and love, especially the last. Believe, hope, and love, especially love, disregarding all obstacles; love God above everything and your neighbor as yourself. If you have not sufficient strength to preserve in your heart these inestimable treasures, fall down more often at the feet of the God of Love. Ask, and it shall be given you; seek and ye shall find; knock and it shall be opened unto you, for He Who has promised is true. Walking, sitting, lying down, conversing, or working, at every time, pray with your whole heart that faith and love may be given to you. You have not yet asked for them as you should ask - fervently and instantly - with the firm purpose of obtaining them. Say now, 'I will begin to do so henceforth.'
Fasting is acceptable to God when abstention from food is accompanied by refraining from sins, from envy, from hatred, from calumny, from vainglory, from wordiness, from other evils. He who is fasting the true fast `that is agreeable' to God ought to shun all these things with all his strength and zeal, and remain impregnable and unshakeable against all the attacks of the evil one that are planned from that quarter. On the other hand, he who practices abstention from food, but does not keep self-control in the face of the aforesaid passions, is like unto one who lays down splendid foundations for a house, yet takes serpents and scorpions and vipers as fellow-dwellers therein.
If some Christians cannot comprehend our Orthodox faith, its Sacraments, it proves that the minds and hearts of such persons are too impure and passionate to bear its purity and brightness, just as sick eyes cannot bear the light of the sun. This heavenly treasure can only be comprehended by the hearts of those who free their minds and feelings from worldly attachments.