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.
At your work, flee conversation; only measured words in case of need. The hands should work for the needs of the body, and the mind should say the sweetest name of Christ, so that the need of the soul, which we must not forget even for moment, also will be provided for.
At this point the zealous man looks inward, and what do you think he finds there? Ceaseless wandering of thoughts, constant onslaughts from the passions, hardness and coldness of heart, obstinacy and disobedience, desire to do everything according to his own will. In a word, he finds everything within himself in a very bad state. And seeing this, his zeal is inflamed, and he now directs strenuous efforts to the development of his inner life, to controlling his thoughts and the dispositions of his heart. From directions on inner spiritual life he discovers the necessity of paying attention to oneself, of watching over the movements of the heart. In order not to admit to anything bad, it is necessary to preserve the remembrance of God. And so he sets to work to achieve this remembrance. But his thoughts can no more be arrested than the wind; his bad feelings and worthless impulses can no more be evaded than the stench of a corpse; his mind, like a wet and frozen bird, cannot rise to the remembrance of God. What is to be done? Be patient, they say, and go on working. Patience and labor are exercised, but all within remains the same. At last someone of experience is found who explains that all is inwardly in disorder because the forces within are divided: mind and heart each go their own way. Mind and heart must be united; then wandering of thoughts will cease, and you will gain a rudder to steer the ship of your soul, a lever by which to set in movement all your inner world. But how can one unite mind and heart? Acquire the habit of praying these words with the mind in the heart, 'Lord Jesus Christ, Son of God, have mercy upon me'. And this prayer, when you learn to perform it properly, or rather when it becomes grafted to the heart, will lead you to the end which you desire. It will unite your mind with your heart, it will cut off your wandering thoughts, and give you the power to govern the movements of your soul.
You ask, 'Must one do something?' Of course one must! And do whatever comes along-in your circle of friends and in your surroundings-and believe that this is and will be your real work. More will not be demanded of you. It is a great misconception to think, whether for the sake of heaven or, as the modernists put it, to 'make one's mark on humanity,' that one must undertake great, reverberating tasks. Not at all. It is necessary only to do everything according to the commandments of God. Just what exactly? Nothing in particular - only those things which present themselves to everyone in the circumstances of life, those things which are required by the everyday happenings we all encounter. Let's take an example: a beggar comes up to you; it is God Who has brought him. God has brought you the beggar, of course, desiring you to act toward this beggar in a manner pleasing to Him, and He watches to see what you will actually do. It will please Him if you help. Will you? If you do what is pleasing to God, you will be taking a step toward the ultimate goal, the inheritance of heaven. Generalize this occurrence, and you will find that in every situation and at every encounter one must do what God wants him to do. And we know truly what He wants from the commandments He has given us. If someone seeks help, then help him. If someone has offended you, forgive him. If you yourself have offended someone, then hasten to ask forgiveness and to make peace. If someone has praised you, do not be proud. If someone has scolded you, do not get angry. If the time has come to pray, then pray. To work, then work, - etc. etc.
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.
If you examine your life well, you will find many instances when God showed His unmistakable mercy to you. Trouble was brewing, but it passed you by for some reason. God delivered you. Acknowledge these and thank God, Who loves you.
The zealous are eager for ascetical struggles of self-forcing and self-opposition with the aim of self-correction, or of raising themselves to primordial purity, so that they might all the more speedily become worthy of communion with God. Obviously the more eager one is, the more diligently and longingly he does this, the sooner he achieves his goal.
Set as a goal the kindling of the fire of the spirit, so that the spiritual fire will burn in your heart and, gathering up all your strength into one, will begin to build your inner man and finally burn up the tares of your sins and passions.
Therefore silence, prayer, obedience; when you practice these virtues with the help of God, then you will know the light of Christ is within your soul.
If the main goal of the repentant sinner should be total, light-bearing and blessed communion with God, then the main hindrance to this is the existence of the passions still active and working in him - the virtues being as yet unsealed in him - and the unrighteousness of his powers. Therefore his main work upon conversion and repentance should be the uprooting of the passions and sealing the virtues - in a word, correcting himself.
If someone should ask: how am I to pray?, the answer is very simple: fear God. Experience of the fear of God arouses attention and consciousness in the heart and forces it to stand with devotion before God.
I am a Christian, you say, and content yourself with this. This is the first deceit - transferring to yourself the privileges and promise of Christianity, without any care to root true Christianity into yourself; or to ascribe to yourself that which can only be acquired by your strength and inner worthiness. Explain to yourself that it is illusory to hope in a name, that God can raise a son of Abraham from a stone and can take away your promise at any time if the conditions for participating in them are not soon fulfilled. Mainly, clarify to yourself what it means to be a Christian, unite yourself to this ideal, and you will see just how stable is this buttress to your blindness.
Let us have recourse to humility on all occasions; for the humble lie prone on the ground, and how can a man fall if he lies on the ground? But a man who stands on a height can easily fall.