As Catholics we know that we have been redeemed through the suffering and death of Jesus Christ. Among other things, this means that we have forgiveness of sins, that we are reconciled to God, and that we have become His adopted children. Jesus' resurrection has won us new life, but it was His sacrificial death that brought about our redemption. Did you know, however, that we can participate in that very redemption through our own suffering? Since God is outside of time, the merits of our suffering can be applied wherever He so desires. We need only to ask.
Perhaps someone has told you to "offer it up", referring to a crisis in your life. Others may even say it jokingly when something trivial annoys us. But every "cross" we bear can have meaning and redemptive value when we unite it to the suffering of Jesus for a noble purpose. St. Paul wrote to the Colossians that he rejoiced in his sufferings for their sake, and in his flesh he fills up what is lacking in the afflictions of Jesus, a rather startling statement since Jesus' sufferings were total and complete. But because the Church is the Body of Christ, St Paul's sufferings were endured on behalf of the whole Body, allowing him to share in Christ's sufferings because of the communion that unites him with the Head of the Body.
In the same way, it is our personal afflictions united to the sufferings of Jesus that can give them meaning and make them redemptive. Acknowledging that what we suffer has a purpose that we believe will some day be made known, we need to courageously accept it and "offer it up" for something like the good of the Church, or for a soul in purgatory, or for relief of temporal punishment due to our sins. As St. Paul writes in Phil 1:29, "For to you has been granted, for the sake of Christ, not only to believe in Him, but also to suffer for Him." Praise the Lord!