22 “Grant me some remission, that I may be refreshed before I go hence”. Consider well, Idithun, consider what knots those are which you would have “loosed” unto you, that you might be “refreshed before you go hence.” For you have certain fever-heats from which you would fain be refreshed, and you say, “that I may be refreshed,” and “grant me a remission.” What should He remit, or loosen unto you, save that difficulty under which, and in consequence of which, you say, “Forgive us our debts.
Grant me a remission before I go hence, and be no more.” Set me free from my sins, “before I go hence,” that I may not go hence with my sins. Remit them unto me, that I may be set at rest in my conscience, that it may be disburthened of its feverish anxiety, the anxiety with which “I am sorry for my sin. Grant me a remission, that I may be refreshed” (before everything else), “before I go hence, and be no more.” For if you grant me not a “remission, that I may be refreshed,” I shall “go and be no more.”
“Before I go” there, where if I go, I shall thenceforth “be no more. Grant me a remission, that I may be refreshed.” A question has suggested itself, how he will be no more....What is meant then by “shall be no more,” unless Idithun is alluding to what is true “being,” and what is not true “being.” For he was beholding with the mind, with which he could do so, with the “mind's eye,” by which he was able to behold it, that end, which he had desired to have shown unto him, saying, “Lord, make me to know mine end.”
He was beholding “the number of his days, which truly is;” and he observed that all that is below, in comparison of that true being, has no true being. For those things are permanent; these are subject to change; mortal, and frail, and the eternal suffering, though full of corruption, is for this very reason not to be ended, that it may ever be being ended without end. He alluded therefore to that realm of bliss, to the happy country, to the happy home, where the Saints are partakers of eternal Life, and of Truth unchangeable; and he feared to “go” where that is not, where there is no true being; longing to be there, where “Being” in the highest sense is!
It is on account of this contrast then, while standing midway between them, he says, “Grant me a remission, that I may be refreshed before I go hence and be no more.” For if Thou “grantest me not a remission” of my sins, I shall go from You unto all eternity! And from whom shall I go to all eternity? From Him who said, I Am HE that Am: from Him who said, “Say unto the children of Israel, I Am has sent me unto you.” He then who goes from Him, in the contrary direction, goes to non-existence....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)