When you receive from Heaven the gift of patience, be attentive and vigilant over yourself, so as to hold and keep within yourself the grace of God, lest sin should creep unnoticed into your soul or body and drive away this grace.
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.
Prayer is a branch (of a tree) of meekness, and freedom from anger. Prayer is an expression of joy and thankfulness. Prayer is a remedy against sorrow and depression.
Do not dare to raise your weak hand to stop the elemental tide of apostasy. Avoid it, protect yourself from it, and that is enough for you. Get to know the spirit of the times, study it so you can avoid its influence whenever possible.
When you shed floods of tears during prayer, do not exalt yourself for this, as though you were above many others. It is that your prayer has received help from above, so that, having zealously confessed your sins, you may incline the almighty to mercy by your tears.
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.