6 With weariness he had pined away; by calling to mind God, he had been delighted, again in babbling he had fainted: what follows? “All mine enemies have anticipated watches”. All mine enemies have kept watch over me; they have exceeded in keeping watch over me; in watching they have been beforehand with me. Where do they not lay traps? Have not mine enemies anticipated all watches? For who are these enemies, but they of whom the Apostle says, “You have not wrestling against flesh and blood.”...Against the devil and his angels we are waging hostilities. Rulers of the world he has called them, because they do themselves rule the lovers of the world. For they do not rule the world, as if they were rulers of heaven and earth: but he is calling sinners the world....With the devil and his angels there is no concord. They do themselves grudge us the kingdom of Heaven. They cannot at all be appeased towards us: because “all mine enemies have anticipated watches.” They have watched more to deceive than I to guard myself. For how can they have done otherwise than anticipate watches, that have set everywhere scandals, everywhere traps? Weariness does invest the heart, we have to fear lest sorrow swallow us up: in joy to fear lest the spirit faint in babbling: “all mine enemies have anticipated watches.” In fine, in the midst of that same babbling, whiles you are speaking, and art speaking without fear, how much is oft-times found which enemies would lay hold of and censure, whereon they would even found accusation and slander— “he said so, he thought so, he spoke so!” What should man do, save that which follows? “I have been troubled, and I spoke not.” Therefore when he was troubled, lest in his babbling enemies anticipating watches should seek and find slanders, he spoke not....
7. “I have thought on ancient days”. Now he, as if he were one who had been beaten out of doors, has taken refuge within: he is conversing in the secret place of his own heart. And let him declare to us what he is doing there. It is well with him. Observe what things he is thinking of, I pray you. He is within, in his own house he is thinking of ancient days. No one says to him, you have spoken ill: no one says to him, you have spoken much: no one says to him, you have thought perversely. Thus may it be well with him, may God aid him: let him think of the ancient days, and let him tell us what he has done in his very inner chamber, whereunto he has arrived, over what he has leaped, where he has abode. “I have thought on ancient days; and of eternal years I have been mindful.” What are eternal years? It is a mighty thought. See whether this thought requires anything but great silence. Apart from all noise without, from all tumult of things human let him remain quiet within, that would think of those eternal years. Are the years wherein we are eternal, or those wherein our ancestors have been, or those wherein our posterity are to be? Far be it that they should be esteemed eternal. For what part of these years does remain? Behold we speak and say, “in this year:” and what have we got of this year, save the one day wherein we are. For the former days of this year have already gone by, and are not to be had; but the future days have not yet come. In one day we are, and we say, in this year: nay rather say thou, today, if you desire to speak of anything present. For of the whole year what have you got that is present? Whatsoever thereof is past, is no longer; whatsoever thereof is future, is not yet: how then, “this year”? Amend the expression: say, today. You speak truth, henceforth I will say, “today.” Again observe this too, how today the morning hours have already past, the future hours have not yet come. This too therefore amend: say, in this hour. And of this hour what have you got? Some moments thereof have already gone by, those that are future have not yet come. Say, in this moment. In what moment? While I am uttering syllables, if I shall speak two syllables, the latter does not sound until the former has gone by: in a word, in that same one syllable, if it chance to have two letters, the latter letter does not sound, until the former has gone by. What then have we got of these years? These years are changeable: the eternal years must be thought on, years that stand, that are not made up of days that come and depart; years whereof in another place the Scripture says to God, “But You are the Self-same, and Your years shall not fail.” On these years this man that leaps over, not in babbling without, but in silence has thought.
8. “And I have meditated in the night with my heart”. No slanderous person seeks for snares in his words, in his heart he has meditated. “I babbled.” Behold there is the former babbling. Watch again, that your spirit faint not. I did not, he says, I did not so babble as if it were abroad: in another way now. How now? “I did babble, and did search out my spirit.” If he were searching the earth to find veins of gold, no one would say that he was foolish; nay, many men would call him wise, for desiring to come at gold: how great treasures has a man within, and he digs not! This man was examining his spirit, and was speaking with that same his spirit, and in the very speaking he was babbling. He was questioning himself, was examining himself, was judge over himself. And he continues; “I did search my spirit.” He had to fear lest he should stay within his own spirit: for he had babbled without; and because all his enemies had anticipated watches, he found there sorrow, and his spirit fainted. He that did babble without, lo, now does begin to babble within in safety, where being alone in secret, he is thinking on eternal years....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)