In her recently republished biography of St. Catherine of Siena (Ignatius Press, 2009), Sigrid Undset offers various insights into the medieval Doctor's celebrated Dialogue.  In the section of her commentary quoted here, Undset focuses specifically on St. Catherine's famous doctrine on the relation of God and man.  Perhaps these words can inform or deeper your Lenten prayer.

The first to whom Catherine told of her spiritual experience in these early years of solitude was Tommaso della Fonte.  He made a mass of notes of what she told him--several volumes full.  They have disappeared, but were used by her biographers Raimondo of Capua and Tommaso Caffarini.  Many of the conversations which she had with her Lord, and which filled her life in these years, she repeated and expounded in the book which she dictated towards the end of her life during several days of almost ceaseless ecstasy, and which came to be known as the Dialogue of Holy Catherine of Siena.  But the fundamental truth uopn which she built her whole life was already revealed to her at this early stage.

One day while Catherine was praying, Jesus appeared to her and said: "Daughter, do you know who you are and who I am?  If you know these two things you will be very happy.  You must know that you are that which is not, but I am That Which Is.  If your soul is possessed of this knowledge the devil will never be able to cheat you, and you shall escape all his snares and all his cunning without suffering.  You will never consent to anything which is against My commands.  Without difficulty you will attain all the gifts of grace and all the virtues of love."

God has created all life out of nothing, and if the mercy of God did not sustain its existence it would immediately return to nothing.  If we are left to ourselves, without the mercy of God, we fall into sin, which is also nothingness.  By ourselves we can neither think of nor achieve anything which is virtuous or good.  It is therefore true that that which is created is in itself nothing.

But because God is the foundation and origin of everything, it is only He Who Is.  As soon as a creature through the light of belief has come to understand this truth he may call himself blessed.  For eternal blessedness consists of this: knowing God as He really is.  As Jesus said to Catherine's namesake, the virgin martyr of Alexandria, when He visited her in prison: "My daughter, know thy Creator."

It seemed to Catherine that once a soul is possessed of this truth it ought to receive willingly and patiently everything which seems hard and bitter, out of love of the Highest Good who created us from nothing, and who from His boundless mercy offers us, whom He has raised from nothingness, eternal bliss in His own kingdom.  (St. Catherine of Siena, p. 40-41)