Human suffering entered the world due to the effects of original sin. God does not cause the suffering. He simply permits it to happen in our lives. To understand suffering, we must first understand some basic principles about God.
God is all-knowing. He is aware of every pain we feel and every tear we shed. He can see our entire life on earth as well as our eternal destiny. God is all-loving. He loves us more than we love ourselves and would not permit something to happen to us that would keep us from our ultimate good, which is God himself. God is all-powerful. He can bring good out of evil.
Bearing these facts in mind, sometimes God permits suffering to keep us from a greater suffering later or to preserve us for a greater good. For example, you might be passed over for a seemingly great job opportunity, only to get a better one later. Or God may know a danger lurking in the job environment that could bring you physical or spiritual harm. Trusting in God helps us deal with this kind of suffering.
Sometimes God permits us to suffer the consequences of our behavior. If we are sexually promiscuous, we might suffer disease, broken relationships, and other problems caused by our behavior. This suffering brings about good when we change our lives and abide by God's laws.
Further, God permits us to lose things that we have come to worship above him. For example, someone who has made money his god may suffer the shame and hardship of bankruptcy. This suffering can bring about a total dependence on God and submission to his will.
God may allow suffering that has no apparent reason--a child dies, we are injured in a car accident, or a natural disaster strikes. These situations are the most difficult to understand. Yet though we do not see the reason for such suffering we know that there is one, even if it is not apparent from our limited perspective.
We are particularly vulnerable and weak when we suffer because we recognize that we are not in control. Yet it is precisely at this moment that we can become our strongest, if we learn to depend on God. Christ died to save us from the loss of heaven. He did not die to save us from suffering in this world.
Yet suffering need never be in vain. St. Paul says, "Now I rejoice in my sufferings for your sake, and in my flesh I complete what is lacking in Christ's afflictions for the sake of the body, that is the church . . . " (Col 1:24). We can join our suffering with Christ's for the sake of others. In this way suffering becomes redemptive. It is not suffering but our response to it that makes it so.