In order to remain in vigilance, it is necessary to guard the freshness and brightness of the mind with all care. The mind becomes darkened from imprudent use of food, drink and sleep, from much talking, from distraction and from worldly cares. Attend to yourselves, said the Lord, be on your guard and take care that your hearts are never weighed down, dulled and depressed by self-indulgence, overeating and drinking, or worldly cares and pleasures, lest that day (the day of Christ's dread judgment, the last day of the world) catch you unawares. For it will spring like a trap upon all who are living on the face of the earth. So watch and pray at all times for the strength to escape or survive all that is going to happen, and to stand before the Son of Man.
The power given by the Lord to His seventy disciples is given to all Christians (Mk. 16:17). Use it, Christian! With the name of Jesus cut off their heads, that is the first appearances of sin in our thoughts, fancies and feelings. Destroy within you the devil's rule over you; destroy all his influence over you; acquire spiritual freedom. The foundation for your struggle is the grace of holy baptism; your weapon is prayer in the name of Jesus.
Watch constantly, learning to understand God's law, for this warms the heart with heavenly fire. Guard your lips from the idle word, or empty talk, lest the heart gets used to evil words.
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.
Prayer requires the inseparable presence and cooperation of the attention. With attention, prayer becomes the inalienable property of the person praying; in the absence of attention, it is extraneous to the person praying. With attention, it bears abundant fruit; without attention, it produces thorns and thistles. The fruit of prayer consists in illumination of mind and compunction of heart; in the quickening of the soul with the life of the Spirit. Thorns and thistles are a sign of deadness of soul and pharisaical self-esteem which springs from the hardening of a heart which is contented and elated by the quantity of the prayers and the time spent in reciting those prayers.
The old man was asked, 'What is the good of the fasts and watchings which a man imposes on himself?' and he replied, 'They make the soul humble. For it is written, Consider my affliction and my trouble, and forgive all my sins' (Psalm 25:18). 'So if the soul gives itself all this hardship, God will have mercy on it.' The old man was (also) asked, 'What should a man do in all the temptations and evil thoughts that come upon him?' The old man said to him, 'He should weep and implore the goodness of God to come to his aid, and he will obtain peace if he prays with discernment. For it is written, 'With the Lord on my side I do not fear. What can man do to me?' (Psalm 118:6).
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.