From Pope John Paul II’s Apostolic Letter on suffering, Salvifici Doloris:
Suffering, in fact, is always a trial—at times a very hard one—to which humanity is subjected. The gospel paradox of weakness and strength often speaks to us from the pages of the Letters of Saint Paul, a paradox particularly experienced by the Apostle himself and together with him experienced by all who share Christ’s sufferings. Paul writes in the Second Letter to the Corinthians: “I will all the more gladly boast of my weaknesses, that the power of Christ may rest upon me”(72). In the Second Letter to Timothy we read: “And therefore I suffer as I do. But I am not ashamed, for I know whom I have believed”(73). And in the Letter to the Philippians he will even say: “I can do all things in him who strengthens me”(74).
Those who share in Christ’s sufferings have before their eyes the Paschal Mystery of the Cross and Resurrection, in which Christ descends, in a first phase, to the ultimate limits of human weakness and impotence: indeed, he dies nailed to the Cross. But if at the same time in this weakness there is accomplished his lifting up, confirmed by the power of the Resurrection, then this means that the weaknesses of all human sufferings are capable of being infused with the same power of God manifested in Christ’s Cross. In such a concept, to suffer means to become particularly susceptible, particularly open to the working of the salvific powers of God, offered to humanity in Christ. In him God has confirmed his desire to act especially through suffering, which is man’s weakness and emptying of self, and he wishes to make his power known precisely in this weakness and emptying of self. This also explains the exhortation in the First Letter of Peter: “Yet if one suffers as a Christian, let him not be ashamed, but under that name let him glorify God”