The question is why would an all-loving God require use of suffering.
I’m just going to take a shot without worrying so much about detailed precision or organization here. I hope I hit your concern and don’t advance anything untrue.
First, I think suffering is more a natural result of enduring sin, separation from God, and all its destructive effects. Original sin is an unchangeable fact of human existence; our perfect natures were corrupted, and so our default position bears a degree of sinfulness and separation. The separation causes pain to us.
Now, we may take on that natural pain of human existence, i.e., we can attempt to cure ourselves of it by making the incredibly difficult turn back to God and enduring its trials, directly bearing the weight of evil, yet refusing to settle with sin. And we will defeat it by lovingly accepting God’s grace. The greatness of suffering is that a love which is willing to endure trials and pain is not only initially greater than a simple, untried love; it’s gradually strengthened by withstanding the hardship, to a point that’s, in the end, even more magnificent than an originally pristine soul would possess, due to its being even stronger. God rejoices more at the return of one sheep that was lost than He does for the sheep that had never strayed.
Or we can run from the pain, which turns out to be impossible. Avoiding suffering is basically a refusal to own up to our sin and acknowledge it for what it is. Flee suffering, say by seeking comfort in worldly success or distraction, and you end up with more sin and thus more drastic pains of separation. The paradox is that, in the acceptance of suffering, one actually ends up causing himself less of it, though that’s hardly a legitimate reason to do it.
The character of the sufferings differ. I’d expect the holy man who embraces suffering to be defying his corrupt desires toward self-interest, popularity, worldly pleasures, etc., meaning that his pain is really from his perverted distaste for the good. (I think of how the demon in ‘The Exorcist’ can’t bear holy water; it physically hurts.) His pain is that of healing and transformation, sort of like undergoing chemotherapy. Our default corruption makes us born to instinctively, but inordinately desire that which will continue us down the path of sin, and resisting that drive feels like being twisted and torn in two. (After the Fall, our rational and animal capacities were disoriented and turned upside down: instead of the lower being directed by the higher, the higher became turned toward subjection to the lower, so that our default orientation is pointing further downward into sin. That’s why the person who refuses to suffer is only causing himself even more suffering. He’s diving right into the source by his very aim to run away.)
So I’m not sure God sort of arbitrarily determined that coming into a renewed relationship with Him should be painful and unenjoyable (though He’d probably be so “justified,” considering we deserve to be punished for our sin, assuming, per impossibile, that God even requires justification for His Will.) Suffering seems to be a necessary condition and effect of realigning ourselves with His Will, away from ours, and letting Him heal us from our self-inflicted wounds. Follow Christ. So take up your Cross and don’t be afraid of a little or a lot of worldly suffering. (Or of voluntarily taking on the burden of someone else’s sin! Feel free to take mine.)
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