St. Augustine and his mother
St. Monica (1855),
The Louvre, Paris.
St. Augustine, In epistulam Johannis ad Parthos tractatus decem 4.6 (407), trans. Burnaby (LCC 8, 290), underscoring mine. Also WSA III.13; FC 92; NPNF 7. Latin: SC 75, 230, 232. Also NBA 24/2; ed. Reale (1994); PL 35, cols. 2008-2009.
This comes out in the Liturgy of the hours (Office of Readings for the Sixth Week in Ordinary Time?) as
The entire life of a good Christian is in fact an exercise of holy desire. You do not yet see what you long for, but the very act of desiring prepares you, so that when he comes you may see and be utterly satisfied.
Suppose you are going to fill some holder or container, and you know you will be given a large amount. Then you set about stretching your sack or wineskin or whatever it is. Why? Because you know the quantity you will have to put in it and your eyes tell you there is not enough room. By stretching it, therefore, you increase the capacity of the sack, and this is how God deals with us. Simply by making us wait he increases our desire, which in turn enlarges the capacity of our soul, making it able to receive what is to be given to us.
So, my brethren, let us continue to desire, for we shall be filled.