4 “O Lord God of virtues, how long will You be angry with the prayer of Your servant?”. Now Your servant. You were angry at the prayer of Your enemy, will You still be angry with the prayer of Your servant? You have converted us, we know You, and will You still be angry with the prayer of Your servant? You will evidently be angry, in fact, as a father correcting, not as a judge condemning. In such manner evidently You will be angry, because it has been written, “My son, drawing near unto the service of God, stand thou in righteousness and in fear, and prepare your soul for temptation.” Think not that now the wrath of God has passed away, because you have been converted.
The wrath of God has passed away from you, but only so that it condemn not for everlasting. But He scourges, He spares not: because He scourges every son whom He receives. If you refuse to be scourged, why do you desire to be received? He scourges every son whom He receives. He who did not spare even His only Son, scourges every one. But nevertheless, “How long will You be angry with the prayer of Your servant?” No longer your enemy: but, “You will be angry with the prayer of Your servant,” how long?
There follows: “You will feed us with the bread of tears, and wilt give us to drink with tears in measure”. What is, “in measure”? Hear the Apostle: “Faithful is God, who does not suffer you to be tempted above that you are able to bear.” The measure is, according to your powers: the measure is, that you be instructed, not that thou be crushed.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)