How it is sometimes to our advantage to be left by God.
But the blessed David recognizes that sometimes this departure of which we have spoken, and (as it were) desertion by God may be to some extent to our advantage, so that he was unwilling to pray, not that he might not be absolutely forsaken by God in anything (for he was aware that this would have been disadvantageous both to himself and to human nature in its course towards perfection) but he rather entreated that it might be in measure and degree, saying “Forsake me not utterly” as if to say in other words: I know that you forsake your saints to their advantage, in order to prove them, for in no other way could they be tempted by the devil, unless they were for a little forsaken by You. And therefore I ask not that You should never forsake me, for it would not be well for me not to feel my weakness and say “It is good for me that You have brought me low” nor to have no opportunity of fighting. And this I certainly should not have, if the Divine protection shielded me incessantly and unbrokenly. For the devil will not dare to attack me while supported by Your defence, as he brings both against me and You this objection and complaint, which he ever slanderously brings against Your champions, “Does Job serve God for nought? Have you not made a fence for him and his house and all his substance round about?” But I rather entreat that You forsake me not utterly— what the Greeks call ἕως σφόδρα, i.e., too much. For, first, as it is advantageous to me for You to forsake me a little, that the steadfastness of my love may be tried, so it is dangerous if You suffer me to be forsaken excessively in proportion to my faults and what I deserve, since no power of man, if in temptation it is forsaken for too long a time by Your aid, can endure by its own steadfastness, and not immediately give in to the power of the enemy's side, unless You Yourself, as You know the strength of man, and moderatest his struggles, “Suffer us not to be tempted above that we are able, but makest with the temptation a way of escape that we may be able to bear it.” And something of this sort we read in the book of Judges was mystically designed in the matter of the extermination of the spiritual nations which were opposed to Israel: “These are the nations, which the Lord left that by them He might instruct Israel, that they might learn to fight with their enemies,” and again shortly after: “And the Lord left them that He might try Israel by them, whether they would hear the commandments of the Lord, which He had commanded their fathers by the hand of Moses, or not.” And this conflict God reserved for Israel, not from envy of their peace, or from a wish to hurt them, but because He knew that it would be good for them that while they were always oppressed by the attacks of those nations they might not cease to feel themselves in need of the aid of the Lord, and for this reason might ever continue to meditate on Him and invoke His aid, and not grow careless through lazy ease, and lose the habit of resisting, and the practice of virtue. For again and again, men whom adversity could not overcome, have been cast down by freedom from care and by prosperity.
Source: Conferences (New Advent)