You raise an eternal question that has challenged the faith of saints, baffled the minds of philosophers and theologians, and created not a few atheists--a question that has no fully adequate answer.
First, we suffer because we are part of a vast creation defined by constant movement, change, decay, death and new life. No creature from the tiniest bacteria to the biggest galaxy is exempt from this cosmic, fluid reality in which we can suffer anything from the common cold to a devastating hurricane, a sprained ankle because of a misstep to an airplane tragedy because of human or mechanical failure. All these are aspects of an imperfect universe and human limitations.
Ancient philosophers pictured suffering as sparks flying out from the cosmic anvil on which new worlds were fashioned. Religious thinkers have considered suffering as part of a "fallen" world alienated from God, subject to corruption and death, yet destined for eventual renewal in glory.
This kind of suffering might be thought of as random or "blind," but we also suffer because of evil intentionally inflicted by others. This is the fundamental cause behind conflict, injustice, exploitation, wars, and what has generally been called "man's inhumanity to man."
According to Christian thought, evil is a perversion of whatever is good, a parasite in the world. Evil is not a creation of God but is the work of God's creatures, who make life a hell for themselves, personally and corporately, when they refuse to live under God's rule of love, preferring to act on their pride, greed, lust, fanaticism, aggression, vengeance, etc.
Why does a loving, good, and perfect God permit such evil to be inflicted on the innocent and the guilty alike? The only morally tolerable explanation must be God's respect for human freedom. The evil exercise of the gift of freedom is responsible for much of the suffering in the world.
No one has the privilege of either being exempt from suffering or coming up with a fully satisfactory solution to the mystery. Jesus himseslf seems to question the value of suffering for a moment in Gethsemane, when he says "Let this cup pass from me." But his next words, "Not my will, but yours, be done," acknowledge that God's plans are perfect, even when humanly unfathomable.
The more crucial and practical issue is how to face suffering personally and socially. If we respond to suffering with faith, moral courage, love, and mutual help, rather than with unbelief, bitterness, and cynicism, we will see that suffering can be redemptive and ennobling--by God's grace and power.
Whatever value we find in suffering can never explain or justify the cost of great pain. Yet when suffering, it is best not to collapse into anger, self-pity, or skepticism, but rather to use suffering itself to lead us closer to God and to each other. "We rejoice in our sufferings, knowing that suffering produces endurance, and endurance produces character, and character produces hope, and hope does not disappoint us, because God's love has been poured into our hearts through the Holy Spirit" (Romans 5:3-5).