Letters of St. Macarius of Optina.

I repeat you about the prayer that the very thought to have the action of grace from the warmth is already delusion: the kingdom of God cometh not with observation (Luke 17, 20). Prepare your heart by fullfillment of the commandments of God, cleansing it from passions, and descend into the deepest humility, learning and seeing your weakness; and when you have the guarantee of humility in your heart, it will be already safe from the delusion of the enemy and the grace of God itself will write its own laws in it. The Saints, who had grace in themselves, considered themselves as not having reached it, and this very humility kept them safe; and who thought to have grace was driven by pride and was deluded…

St. Isaac the Syrian. "Ascetic Words." Word 55.

One of the saints wrote: "If one does not consider himself a sinner, his prayer is not accepted by the Lord." If you say that some fathers wrote, what is purity of heart, what is health, what is dispassion, what is contemplation, they wrote not in order to make us strive for that ahead of time; for it is written that the kingdom of God cometh not with observation (Lk.17: 20) of expectation. And those who had such intention, they obtained pride and fall. And we will arrange the region of the heart by repentance and life pleasing to God; what is given by the Lord comes by itself, if the place in the heart is pure and undefiled. What we are looking for with observation, I mean high Divine gifts, is not approved by the Church of God; and those who accepted that, they obtained pride and fall. And this is not a sign that a person loves God, but mental illness. And how can we strive for high Divine gifts, when Paul glories in tribulations and considers the fellowship of the sufferings of Christ to be a high God's gift.

Saint Nectarios of Aegina. "The Way to Happiness." Reasoning.

Saint Nectarios of Aegina

I wish you have the reasoning and wisdom. Avoid extremes. The strictness of your life should be consistent with the measure of [your] virtue. One who wants to compete with the perfect ones [at once] and live as the holy ascetics [lived], will most likely, become proud and fall. So strive wisely and do not exhaust the body with overwork. Remember that restraining of the flesh is only a tool to help the soul to attain perfection, and the spiritual warfare of the soul itself is the most important.

Do not impose on yourself more than you can bear. Remember that God cannot be forced when he delivers his gifts, but He gives when He wants it. You receive undeservingly all that He gives you, [only] on His mercy.

Do not think that you will get higher gifts and virtues for your great works, - [thinking] so, you get the risk of falling into pride. One who seeks divine gifts and insights, while being wrapped up in the passions, is in the foolish and proud delusion. First, one needs to work on purifying oneself. Grace is sent as a gift to those who are cleansed from the passions. And they get it quietly and in an hour that they are not aware of.  

Saint Ambrose of Optina

The Letters of Saint Ambrose of Optina.

You are writing that on the eve of Archangel Michael Feast, a fiendish thought came to you, promising all spiritual gifts on the Feast, but instead of this a gloomy anguish seized you and suicide intention disturbed you greatly. Here are demonic gifts, enemy delusion! The thought whispers to you that none of the Saints and those desiring salvation were fighting with this thought. It is not true: great elders were fighting with it too; in Moldova, there was a very ascetic and silent elder, who suffered all his life with this thought. In this severe evil attack you must often repeat: “Let it be God's will for my life. Let it be as God wants." The Lord's will is to save and have mercy upon all believers. We can sometimes answer to the enemy like this: "Come after me, Satan: I will work all the days of my life for the Lord, my God. As to Whom are due all glory, honor and worship as to His Eternal Father and All-Holy and Good and Life-giving Spirit to the ages of ages. Amen."