To balance the, let's face it, terrifying message of the sermon below (admittedly, St. Leonard exempted pious souls from the message, directing it towards the lukewarm and halfhearted Christian, and the obstinate sinner), I thought it would be a good idea to set forth some quotations from St. Faustina's diary, which records private revelations she received directly from Our Lord. The diary was one of only two books Pope John Paul II requested when he lay recovering in the hospital from his bullet wounds (the other was the Bible).

I desire that priests proclaim this great mercy of Mine towards souls of sinners. Let the sinner not be afraid to approach Me. The flames of mercy are burning Me - clamouring to be spent; I want to pour them out upon these souls....Distrust on the part of souls is tearing at My insides. (50)

Today I am sending you with My mercy to the people of the whole world. I do not want to punish aching mankind, but I desire to heal it, pressing it to My Merciful Heart. I use punishment when they themselves force Me to do so; My hand is reluctant to take hold of the sword of justice. Before the Day of Justice I am sending the Day of Mercy. (1588)

Write, speak of My mercy. Tell souls where they are to look for solace; that is, in the Tribunal of Mercy. There the greatest miracles take place [and] are incessantly repeated. To avail oneself of this miracle, it is not necessary to go on a great pilgrimage or to carry out some external ceremony; it suffices to come with faith to the feet of My representative and to reveal to him one's misery, and the miracle of Divine Mercy will be fully demonstrated. Were a soul like a decaying corpse so that from a human standpoint, there would be no [hope of ] restoration and everything would already be lost, it is not so with God. The miracle of Divine Mercy restores that soul in full. Oh, how miserable are those who do not take advantage of the miracle of God's mercy! You will call out in vain, but it will be too late. (1448)

Every time you go to confession, immerse yourself in My mercy, with great trust, so that I may pour the bounty of My grace upon your soul. When you approach the confessional, know this, that I Myself am waiting there for you. I am only hidden by the priest, but I myself act in your soul. Here the misery of the soul meets the God of mercy. Tell souls that from this fount of mercy souls draw graces solely with the vessel of trust. If their trust is great, there is no limit to My generosity. The torrents of grace inundate humble souls. The proud remain always in poverty and misery, because My grace turns away from them to humble souls. (1602)