Well, really, all of the above. Suffering can be a helpful punishment for sin, but it is also a trial we undergo in union with Christ, who “bore our sufferings,” and it is perhaps one of the most powerful ways to practice faith in a practical manner. Faith in God’s love and care for us while we suffer is a very effective way of growing in love for God, which is really the whole point of our religion, after all.
We have faith in the teachings of the creeds of the Catholic Church, which we recite at Mass on Sunday and when we pray the rosary, but faith in the midst of our own woes and pains and sorrows is a very personal faith, whereby we unite ourselves to Christ’s mysterious plans for us. We belong to him, we are members of him as limbs of the body to their head, and so when we suffer, our faith strengthens our union with him in love.
Think of it this way: the only reason I feel a pain in my leg or arm is because they are united to my head and receive the perception of pain from there. So too my suffering is a sign of my union with my spiritual Head, the Savior. This is true also of my pleasures, but it is sometimes hard to remember our need to depend on him when we are enjoying ourselves. But when we suffer, we are reminded. Let us not be afraid to bear our crosses with faith!