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.
There is a sin which is always 'unto death' [1 Jn 5:16]; the sin which we have not repented. Even a saint's prayers will not be heard for the unrepented sin. The person who repents correctly does not imagine that his sins are cancelled through his own effort; but knows that through this effort he makes peace with God.
He who reveres the Lord does what is commanded, and if he commits some sin or disobeys Him, endures whatever he has to suffer for this as being his desert.
Meekness and humility of heart are virtues without which it is impossible to inherit the Heavenly Kingdom, to be happy on earth, or to experience inner calm.
Peace of soul is acquired by perfect surrender to the Divine Will, without which nothing happens... He, in whose heart humility and meekness are reborn, will find true rest for his soul. He will be satisfied with everything, grateful for everything, peaceful and full of love for everybody. He will judge none and will feel no anger. His heart will be filled with divine sweetness, that is, he will feel in himself the Kingdom of God because God grants His grace only to the humble.