JPII on Suffering
Faith in the fact that we are sharing in the sufferings of Christ, [Pope] John Paul II says, gives a person "the certainty that in the spiritual dimension of the work of Redemption HE IS SERVING, like Christ, THE SALVATION OF HIS BROTHERS AND SISTERS. Therefore he is carrying out an irreplaceable service. In the Body of Christ, which is ceaselessly born of the Cross of the Redeemer, it is precisely suffering permeated by the spirit of Christ's sacrifice that is THEIR REPLACEABLE MEDIATOR AND AUTHOR OF THE GOOD THINGS which are indispensable for the world's salvation. It is suffering, more than anything else, which clears the way for the grace which transforms human souls. Suffering, more than anything else, makes present in the history of humanity the force of the Redemption" ("Salvifici Doloris",27).
Navarre Bible Commentary on Colossians 1:24-2:3