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."
Praise and thanksgiving to the Lord that after this fight He soon comforted you. But different confusing thoughts trouble you again. You ask me to solicit God's grace, which will allow you in a full consciousness consider yourself the worstе and the most sinful than anyone in the monastery; and then you write that if you are given a roommate, you will retire, and that you prayed to the Queen of Heaven that if She wanted you to end your life here then you should not be given a roommate. It's you yourself that made such a condition, you decided. If you want to get rid of pride and self-conceit, you primarily need to submit to God’s will. If you want everything to be by the will of God, then suffer everything and not invent enemy conditions, don’t go into the enemy net yourself. And look, what imprudence is to run from one roommate and come to the convent full of sisters, where fewer than four people do not live in the same cell. I wrote and said to you before and I repeat now, that complete solitude is not only useless for you, but also dangerous. Do you see yourself, how fierce enemy attacks you encounter in your solitude! What a trouble if you are given a roommate? Maybe you will get more relief through her in your spiritual warfare. Do not accept responsibility for her and take her on the terms that she will live at her expense, sit in the anteroom and be silent; and take her only on these terms; while do not take a young roommate, for which you need to be responsible. If you are given one that is not suitable for you, then you can tell them to give you another, you are not voiceless.
Do not trust to any visions. Saint Gregory of Sinai says: "Never let you trust, if you see anything sensually, or intellectually, or outside or inside or if you dream about or imagine Christ, an Angel, or a Saint, or light, because the mind by its nature can easily dream and imagine as it wants; and those who trust visions harm themselves. Also the memory about good and evil things usually suddenly shows images in the mind what sets the mind to dreaming and makes a person a dreamer but not a hermit. So try not to believe anything … but be indignant at this, keeping your mind from visions and imaginations. The novice should pay attention only to the non-delusional action of the heart, not accepting anything else until the time of subsidence of passions. The Lord is not indignant at person looking cautiously at himself because of the danger of delusion; even if this man will not accept something from Him, unless asking and lots of testing, but God more praises him as a wise one… It is very necessary to reach the truth truly and to be clear from the enemy of the grace, as the Devil in the form of truth usually shows his delusion in the novices, displaying the cunning as the spiritual". Here is what St. Gregory of Sinai says, remember it, and stick to it firmly. You write that you somehow felt that the light flashed from above, that it was shiny from the words of the Jesus Prayer, and so on. Do not trust to anything of this, all this is dreaminess, which should be rejected. In all your temptations try to hold the prayer. If you can not say it completely, i.e. all words of the Prayer of Jesus, then you can say, "Jesus, Jesus," it is not forbidden, and the Holy Fathers did not reject it. "Flog your enemies with the name of Jesus" - says the Climacus. The power of this name is great.