April 18th
Book Four, Chapter 12
With How Great Diligence he Who is to Communicate Ought to Prepare Himself for Christ

I am the Lover of purity and the Giver of all sanctity.  I seek a pure heart, and there is the place of My rest....If you will have Me to come to you and remain with you, purge out the old leaven, and make clean the habitation of your heart.  Shut out the whole world and all the tumult of vices; sit as a sparrow solitary on the house-top, and think of your excesses in the bitterness of your soul....

But you ought not only to prepare yourself for devotion before Communion, but also carefully to keep yourself therein after the reception of the Sacrament.  Neither is watchfulness less required after, than a devout preparation before; for strict guardianship afterwards is the best preparation for again obtaining a greater grace....Beware of much talk; remain in secret and enjoy your God; for you have Him whom all the world cannot take from you.  I am He to whom you ought to give your whole self; so that henceforth you may live not in yourself, but in Me, and free from all solicitude.