The following comes from Irenaeus' Demonstration of the Apostolic Teaching, from the second century:
Now this world is encompassed by seven heavens, in which dwell powers and angels and angels and archangels, doing service to God, the Almighty and Maker of all things: not as though He was in need, but that they may not be idle and unprofitable and ineffectual.
In my mind, this is closely linked to Pascal’s teaching that prayer was given to us so that we might have "the dignity of causality," as well as Lewis’ poem about prayer, that says that when we pray, “for a moment, He enfeebles His power.” I believe that a strong case can be made that if we are invited to partake in the redemption of the world, through our suffering, it is not because Christ is in need, but rather it is a gift given to us that we “may not be idle and unprofitable and ineffectual.” The redemption of the world comes solely through Christ, but through his grace, He allows us to carry our daily cross on behalf of the rest of the world, as Colossians 1:24 teaches. This is a hard sell for a lot of Protestants, but C.S. Lewis believed it, Elisabeth Elliot believes it, and so do a lot of other Protestants, including me.
I stumbled on a quote from Jane Eyre a day or two ago:
I cannot deny that I grieved for his grief, whatever that was, and would have given much to assuage it.
Everyone has said something similar in our lives about someone we love. That's the love of Christ reflected through us, and it finds its most noble expression in being willing to lay down our life for a friend, just as Christ did. Though today that rarely takes the form of actual death, there are examples where this is exactly what God allowed. The most poignant example that I can think of is from A Severe Mercy, where Davy offered her life on behalf of her husband, Sheldon Van Auken. God viewed her as a "living sacrifice, holy and acceptable," and it was through the "severe mercy" of her death that Sheldon came fully to Christ.
We can endure almost anything, when we believe that by enduring it, we can somehow "assuage" another's grief, and even more so, when we know that we would do anything to work with Christ for another's redemption. Whenever we sacrifice anything, for anyone, we are closest to who we are as children of God, made in His image, in the image of perfect Love. Mother Theresa's example is a powerful one. From Come By My Light: "She had insisted that it would be 'worth going through every possible suffering just for one single soul.'" Mother Theresa carried much pain and despair in her life, and continually offered it up on behalf of the poor and lost in Calcutta, and counted it as worth the cost.
In his book, Man's Search for Meaning, Viktor Frankl relayed a story that took place in a deep moment of despair at the Theresienstadt concentration camp. He was asked by some in his barracks to speak any encouragement that he could. He "told them of a comrade who on his arrival in camp had tried to make a pact with Heaven that his suffering and death should save the human being he loved from a painful end. For this man, suffering and death were meaningful; his was a sacrifice of the deepest significance. He did not want to die for nothing." For the men in the camp, Frankl understood the truth of Nietzche's words, "He who has a why to live for can bear with almost any how."
The most powerful quote I've read on suffering comes from Merton, who proclaims that our suffering is "something demanded by our own personal destiny." It is "the sacramental gift of Christ's love, given to me by God the Father along with my identity and my very name."
Our suffering is unique. We alone can carry it, and to run from it, at all costs, by deadening it in unhealthy ways, is to run away from God's plan for our lives and from the grace which He desires to pour out, in and through us. I am amazed at how Frankl's words resonate so closely with Merton's: "When a man finds that it is his destiny to suffer, he will have to accept his suffering as his task; his single and unique task. He will have to acknowledge the fact that even in suffering he is unique and alone in the universe. No one can relieve him of his suffering or suffer in his place. His unique opportunity lies in the way in which he bears his burden." The call and invitation of Christ is to bear our particular burden, on behalf of our brothers and sisters, just as Mother Theresa--just as Christ did on behalf of us all.