Enduring Afflictions as a Good Work in the Lutheran Confessions
"We have already said that a eucharistic sacrifice does not merit reconciliation but comes from the reconciled, just as afflictions do not merit reconciliation but are eucharistic sacrifices when the reconciled endure them."
Ibid., art. IV.192-93.
"Through these works Christ shows his victory over the devil, just as the distribution of alms by the Corinthians was a holy work (1 Cor. 16.1), a sacrifice, and a battle of Christ against the devil, who is determined that nothing happen to the praise of God. To disparage works like the confession of doctrine, afflictions, works of charity, and the mortification of the flesh would be to disparage the outward administration of Christ's rule among men."
Ibid., art. XXIV.25
"The rest are eucharistic sacrifices, called 'sacrifices of praise': the proclamation of the Gospel, faith, prayer, thanksgiving, confession, the afflictions of the saints, yes, all the good works of the saints."
Ibid., art. XXIV.30, 32
"With the abrogation of Levitical worship, the New Testament teaches that there should be a new and pure sacrifice; this is faith, prayer, thanksgiving, confession and proclamation of the Gospel, suffering because of the Gospel, etc. . . .
"The proclamation of the Gospel produces faith in those who accept it. They call upon God, they give thanks to God, the bear afflictions in confession, they do good works for the glory of Christ. This is how the name of the Lord becomes great among the nations."
I think that we tend to narrow the scope of "afflictions," thinking that they are approved of God only when we're being boiled alive by cannibals. But in the ordinary context of everyday work, Peter writes that submitting to an "unreasonable" boss (not exactly, but close enough) "finds favor, if for the sake of conscience toward God a man bears up under sorrows when suffering unjustly" (1 Peter 2.19).
Or when Paul writes, "never pay back evil for evil" (Ro 12.17), he's talking about ordinary human relationships, not about receiving evil specifically for being a Christian. But, as a Christian, we would receive evil without seeking compensation.
But why suffering? I don't have a complete answer; here are a couple of thoughts.
First, if Jesus was perfected through suffering (Heb 2.10), then it shouldn't be a surprised that the members of his body are perfected through suffering as well. (Not that I entirely understand what that means.) Secondly, we perhaps suffer for other Christians, as Paul did (2 Co 1.3-7). We are also afflicted for our own good (Heb 12.4-11).
More generally, I wonder whether, when we suffer in this world, God is, as it were, only allowing us to see its true nature – that this present world holds nothing in itself but death and uncleanness. This world never mediates life to us – although that is the lie that humans have believed from the beginning. Through suffering, God reveals to us the true nature of this world, thereby teaching us not to trust in it for our life, but to trust only Christ, looking to the world to come, which is where life truly resides in the presence of God. By revealing the reality of the fallen world, afflictions thereby cause us to despise the cheap counterfeit of "life" that this world offers us, and instead directs us to the true life provided by God.