“Whoever asks that one thing of the Lord (Psalm 27:4) and seeks after it asks with certainty and security, without fear that it will do him harm when he obtains it.
Without this, no other thing which he asks as he ought will do him any good when he obtains it. That one thing is the one true and solely happy life, that we may see forever the delight of the Lord, and made immortal and incorruptible in body and soul.
Other things are sought for the sake of this one thing, and are asked for with propriety. Whoever possesses it will have everything he wishes, and will not be able to wish for anything in that state, because it will not be possible for him to have anything unbecoming.
Truly, the fountain of life is found there (Psalm 34:8-10), which we must now thirst for in our prayers, as long as we live in hope, because we do not see what we hope for (Romans 8:25) under the cover of His wings, before whom is all our desire.
We hope to be inebriated with the plenty of His house, and to drink of the torrent of His pleasure, since with Him is the fountain of life, and in His light we shall see light. (Psalm 36:9)
Then our desire shall be satisfied with good things and there will be nothing more for us to seek by our groaning, since we will possess all things to our joy.”
–Augustine of Hippo, “Letter 130 (A.D. 412)” in Letters, Volume 2 (83-130), Trans. Wilfrid Parsons (Washington, D.C.: CUA Press: 1953/2008), 398-398.