I think that, during certain stages of Christian life and experience, pain is always a mystery. And so long it is a grand trial of trust in God's perfect wisdom and love and rightness. "His work is perfect:" Deut. xxxii. 4. (But wait patiently till you have had, first, some years of pastoral work, and, second, some personal experience of great pain; and then you will see.) To myself the whole thing is clear as sunshine, but tenfold clearer since the intense pain through which He has led me of late. I would not have foregone that teaching for anything!
I. Pain, as to outsiders, is no mystery when looked at in the light of God's holiness, and in the light of Calvary. The deeper our views of and hatred of sin (as the Holy Spirit's teaching in our hearts progresses), the more clear will all that is connected with sin become; and as, had there been no sin there would have been no pain, it is all, and more than all, deserved. I can say for myself that I feel I have deserved the very suffering of hell for my transgression of the first great commandment of the law ("thou shall love the Lord thy God," etc.), and for my sin of unbelief.
It is, further, a real proof of God's love. He cannot (being Love) enjoy the sight of suffering, It must be as much worse to Him than to you, as He is infinitely greater and more loving than you! And yet He inflicts or permits it, that He may rouse, and warn, and check, and save. What thousands have blessed Him for the pain that came like a rough hand catching them as they fell over a precipice, hurting and pinching their very flesh, but saving their lives! In how many ways a skilful doctor gives pain, that he may prevent much greater and worse suffering! At the same time, I am quite sure that with very, very rare exceptions bodily pain, though far more trying to witness, is not anything to compare with mental pain, and it leaves no sting or scar, as almost every other form of real trial must do. (I am perhaps in an especially good position to judge of this point, because all my doctors agree in saying that, from my unusually finely strung nerves, I am and always shall be peculiarly sensitive to physical pain, and feel it far more keenly than ordinary people)
II. Pain, as to God's own children, is truly and really, only blessing in disguise. It is but His chiseling, one of His graving tools, producing the likeness to Jesus for which we long. I never yet came across a suffering (real) Christian who could not thank Him for pain! Is not this a strong and comforting fact! I do not say that they always do so during the very moments of keenest pain, though much more often than not I think they are able to do this; but, certainly, they do deliberately praise Him for it afterwards. I think one must pass through it for oneself before one can fully realize the actual blessedness of suffering; meanwhile, you may well take the testimony of those who have. Its conscious effects are to give one deeper feeling of one's entire weakness and helplessness (a lesson which we are all slow to learn in health), and of the real nothingness of earthly aims and comforts, and the fleetingness and unsatisfactoriness of everything except Christ. Then, it drives one to Him each moment, one cannot bear it even one minute alone, one must lean and cling (and anything is blessed which does this!). And then, one finds that He is tender and gracious, that His promises are precious, that His presence is a reality even if unrealized (a true paradox)! Then, one has opportunities which one could not otherwise have of learning trust, and patience, and meekness; it is a time of growing up into Him in these things. Then, one realizes more what it must have been to Jesus to endure real, actual, bodily pain for us. I never saw such tremendous force in 1 Peter ii. 24 ("in His own body") as when suffering great pain myself; it seemed a new page of His love unfolded to me. I could write sheets more on the blessed teachings of pain, but if I did I should perhaps bring it on! So far, the whole question of pain is rather one of sight than of faith to me now; it has become so clear to me, as a part of God's great plan which could not be done without. But I find yet scope for faith beyond. I believe there is a mysterious connection between suffering here and actual capabilities of enjoyment hereafter, and that suffering here is training (I cannot tell how) for that glorious service above, to which I delight to look forward. But now look for yourself at what God's word says about it, and dwell on that instead of on your own thoughts about it, for His thoughts are not as your thoughts; see Isaiah Iv. 8, 9. Look at 2 Corinthians iv. 17, 18; and then see how much more you can find in His word which bears on the subject . . . .
Trust Jesus in and for everything. When a trial is past, one does so bitterly regret not having trusted Him entirely in it; and one sees that we might as well have had all the joy and rest of perfect trust all along.
Frances Ridley Havergal, Memorials, A Letter, pp. 184-187