Here is an excerpt from a manuscript on Purgatory, from a nun in Purgatory talking to another (living) nun.
A suffering soul in purgatory to Sister M. at a cloister in 19th century France (from Unpublished Manuscript on Purgatory):
"If you could only know what I suffer! Pray for me, please. I suffer intensely everywhere. My God, how merciful You are! No one can imagine what Purgatory is like. Be kind and take pity on the poor souls.
"May 1874. I have been in the second Purgatory since the Feast of the Annunciation. On that day I saw the Blessed Virgin for the first time. In the first stage, we never saw her. The sight of her encourages us and this beloved Mother speaks to us of Heaven. While we see her, our sufferings are greatly diminished.
"You do well to pray to St. Michael and to urge others to do so. One is indeed happy at the hour of death when he has had confidence in some of the saints. They will be his protectors before God in that terrible moment.
"Make it a practice to live in the presence of God with a pure intention. God seeks devoted souls who will love Him for His own sake. These are very few. He wants you to be one of His true friends. Many think they love God, but they love Him for their own sakes.
"February 1875. Watch carefully over your interior life. Keep all your small troubles for Jesus alone. He is well able to make up to you for whatever He takes from you. Your life must be one of unceasing interior acts of love and of mortification, but God alone must know of it. Do nothing extraordinary. Lead a very hidden life, yet one closely united to Jesus.
"Love God very much. How happy are the souls that do this. They possess a treasure! The great penance of your life will be, not the absence of your Jesus but great sorrow for all the pain you have given Him, by your failure to love Him as you desire, in return for the overwhelming number of graces which He has showered upon you and which He will continue to shower upon you.
"Love everyone, but do not put your trust entirely in anyone, because Jesus wants to be your great confidant. Everything for Him and for Him alone. Perform all your actions in the presence of God as I have so often told you. Consult Him before all you do or say. Let your life be one of faith and love... Do nothing to distinguish yourself. Without offending anyone, avoid the company of those who are too unreserved and those who are uncharitable. As for yourself, be busy about your own affairs. Keep your opinions to yourself and never express them unless obliged to do so. Be preoccupied with only that one subject, the mainspring of your life, Jesus.
"December 8, 1875. Love God intensely. Do not fear your own suffering. Trust in Him, never in yourself. Die to yourself from morning to night... Do not breathe or live except for Jesus Christ. God must be your only confidant. Complain to no one except for Him. Be quite hidden from the eyes of everyone else.
"Feast of the Annunciation. When God wishes a soul to be entirely His, He begins by crushing it, very much as apples are crushed in the press—to extract its passions, its self-seeking, in a word, all its defects. When a soul is sufficiently broken, He reshapes it according to His will. If it is faithful, it is soon transformed. Only then does Jesus load it with His choicest graces and inundate it with His love.
"Jesus wants you to deal with Him, as with an intimate friend, without any fear whatsoever. It is true that His Majesty is frightening and that you are not worthy to have such intimate converse with your Jesus, but is He not the Master that enriches whomsoever He wills? Ask Jesus to make you rich in every virtue, as He wishes you to be, but in the meantime, shape your life in accordance with His inspirations. Enlarge your heart because what Jesus desires above all things is to see in it His love. What wonderful graces you will receive if you are faithful, graces you have never even thought of.
"May 12th. Mortify yourself corporally, but more especially spiritually. Forget yourself. Deny yourself in everything. Never look at what others are doing. God does not demand the same perfection from everyone. All are not enlightened in the same way, but you, whom Jesus Himself enlightens, look only to Him, let Him be your aim and object in everything.
"Never grow weary in your work. Begin each day as if you had so far done nothing. This continual renouncement of one’s will and comfort and one’s own opinions is a long martyrdom, but it is most pleasing to God. God wants you to be something special, not as regards your exterior, but in your inner soul. He asks of you a union with Himself, so great that you never lose sight of Him, even amidst your absorbing occupations.
"While on earth one truly cannot picture or imagine what God really is, but we (in Purgatory) know and understand Him for what He is, because our souls are freed from all the ties that fettered them and prevented them from realizing the holiness and majesty of God, and His great mercy. We are martyrs, consumed as it were by love. An irresistible force draws us towards God who is our center, but at the same time another force thrusts us back to our place of expiation. We are in the state of being unable to satisfy our longings. Oh, what a suffering that is, but we desire it and there is no murmuring against God here. We desire only what God wants. You on earth, however, cannot possibly understand what we have to endure.
"Be ingenious in mortifying yourself and in breaking your own will. Be especially nice to those who are less agreeable to you than to others, no matter what wrong they may have done to you. This means renouncing yourself and pleasing Jesus. Nothing else matters. It is on these occasions that you must silence the human will, but you must do it because Jesus wills it. Do not allow self-love to get the upper hand, but do all blindly to please Jesus alone."