This reminds me of a segment of St. Augustine's letter to Probus that I read this morning! I was able to find it online: 

25. Perhaps you may still ask why the apostle said, "We know not what to pray for as we ought," for it is wholly incredible that either he or those to whom he wrote were ignorant of the Lord's Prayer. He could not say this either rashly or falsely; what, then, do we suppose to be his reason for the statement? Is it not that vexations and troubles in this world are for the most part profitable either to heal the swelling of pride, or to prove and exercise patience, for which, after such probation and discipline, a greater reward is reserved, or to punish and eradicate some sins; but we, not knowing what beneficial purpose these may serve, desire to be freed from all tribulation? To this ignorance the apostle showed that even he himself was not a stranger (unless, perhaps, he did it notwithstanding his knowing what to pray for as he ought), when, lest he should be exalted above measure by the greatness of the revelations, there was given unto him a thorn in the flesh, a messenger of Satan to buffet him; for which thing, not knowing surely what he ought to pray for, he besought the Lord thrice that it might depart from him.

At length he received the answer of God, declaring why that which so great a man prayed for was denied, and why it was expedient that it should not be done: "My grace is sufficient for thee; my strength is made perfect in weakness."

26. Accordingly, we know not what to pray for as we ought in regard to tribulations, which may do us good or harm; and yet, because they are hard and painful, and against the natural feelings of our weak nature, we pray, with a desire which is common to mankind, that they may be removed from us. But we ought to exercise such submission to the will of the Lord our God, that if He does not remove those vexations, we do not suppose ourselves to be neglected by Him, but rather, in patient endurance of evil, hope to be made partakers of greater good, for so His strength is perfected in our weakness. God has sometimes in anger granted the request of impatient petitioners, as in mercy He denied it to the apostle. For we read what the Israelites asked, and in what manner they asked and obtained their request; but while their desire was granted, their impatience was severely corrected? Again, He gave them, in answer to their request, a king according to their heart, as it is written, not according to His own heart? He granted also what the devil asked, namely, that His servant, who was to be proved, might be tempted.s He granted also the request of unclean spirits, when they besought Him that their legion might be sent into the great herd of swine. These things are written to prevent any one from thinking too highly of himself if he has received an answer when he was urgently asking anything which it would be more advantageous for him not to receive, or to prevent him from being cast down and despairing of the divine compassion towards himself if he be not heard, when, perchance, he is asking something by the obtaining of which he might be more grievously afflicted, or might be by the corrupting influences of prosperity wholly destroyed. In regard to such things, therefore, we know not what to pray for as we ought. Accordingly, if anything is ordered in a way contrary to our prayer, we ought, patiently bearing the disappointment, and in everything giving thanks to God, to entertain no doubt whatever that it was right that the will of God and not our will should be done. For of this the Mediator has given us an example, inasmuch as, after He had said, "Father, if it be possible, let this cup pass from me," transforming the human will which was in Him through His incarnation, He immediately added, "Nevertheless, O Father, not as I will but as Thou wilt." Wherefore, not without reason are many made righteous by the obedience of One."