Train yourself to cut off an intrusive thought immediately…Be at pains over this, so that you acquire the habit. The soul is a creature of habit: according to the habit you have acquired, so will you act all the rest of your life.
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.
The first divine fruit of silence is mourning -- grief according to God -- joy-grief. Afterward come luminous thoughts, which bring the holy flow of tears streaming with life, from which also comes the second baptism and the soul is purified and shines and becomes like the angels.
Mourning has a twofold action: like water tears extinguish all the fire of passions and wash the soul clean of their foulness; and, again, through the presence of the Holy Spirit, it is like fire bringing life, warming the heart, and inciting it to love and desire God.
Be careful not to neglect the small things, take care not to despise them as something insignificant. They are not insignificant; they are cancer for the soul, a bad habit. Let us therefore be vigilant. Let us pay attention to slight things, whilst they are still slight and before they become serious. Both the life of holiness and the sinful life start from little things and lead to greater ones, either good or bad.
Let your very dress urge you to the work of mourning, because all who lament the dead are dressed in black. If you do not mourn, mourn for this cause. And if you mourn, lament still more that, by your sins, you have brought yourself down from a state free of labors to one of labor.
I consider those fallen mourners more blessed than those who have not fallen and are not mourning over themselves; because as a result of their fall, they have risen by a sure resurrection.
When a man has been sufficiently illumined, however, to perceive his own faults, he never ceases mourning for himself and for all men, seeing God’s great forbearance and what sins we in our wretchedness have committed and still persist in committing. As a result of this he becomes full of gratitude, not daring to condemn anyone, shamed by the profusion of God’s blessings and the multitude of our sins. Thereupon he joyfully renounces everything in his own will that is counter to God, and he watches over his own senses, so as to prevent them from doing anything beyond what is unavoidably needed.
If you possess the gift of mourning, hold on to it with all your might. For it is easily lost when it is not firmly established. And just as wax melts in the presence of fire, so it is easily dissolved by noise and bodily cares, and by luxury, and especially by talkativeness and levity.
Habit forms from custom, and habit seems to accustom itself to nature. It is much worse and more difficult to change nature. However, with God it is possible. For nature does not set itself against God.
If you are enclosed within yourself through prayer, humility, and mourning, you will find a spiritual treasure -- only let pride and criticism be far from you.
Those who mourn and those who are insensitive are not subject to fear, but the cowardly often have become deranged. And this is natural. For the Lord rightly forsakes the proud that the rest of us may learn not to be puffed up.
A characteristic of those who are still progressing in blessed mourning is temperance and silence of the lips; and of those who have made progress – freedom from anger and patient endurance of injuries; and of the perfect – humility, thirst for dishonors, voluntary craving for involuntary afflictions, non- condemnation of sinners, compassion even beyond one’s strength. The first are acceptable, the second laudable; but blessed are those who hunger for hardship and thirst for dishonor, for they shall be filled with the food whereof there can be no satiety.