2 Corinthians 4:13-14 features a piece of Paul's own commentary on his apostolic ministry. After highlighting the sufferings wrapped up in his ministry (2 Corinthians 4:8-10), he quotes a portion of Psalm 116 and identifies himself as having the same "spirit of faith."
This "spirit of faith" is explained by Paul in verse 14 as hope in the resurrection and is confirmed in the context of Psalm 116—which also includes suffering (Psalm 116:3-4) and psalter-fashioned resurrection language (Psalm 116:8-9). A paraphrase of Paul's thought would be something like:
Yes, a great deal of hardship accompanies our ministry to you. But our ministry is in the same spirit as Psalm 116. In the midst of his suffering, the psalmist hoped in the resurrection and so do we. We know that just as God raised up Jesus from the dead he will raise us up, too, and he will bring us together into his presence.
This all leads to 2 Corinthians 4:15. Verse 15 begins as a ground to Paul's ministry—"For it is all for your sake"—and then moves to the purpose: "so that as grace extends to more and more people it may increase thanksgiving, to the glory of God."
In one verse we go from the lofty clouds of Paul's psalmist-shared, resurrection-envisioning ministry to the pavement of people who are grateful for the gospel. The connection between the clouds and the pavement is purpose. And the purpose is thanksgiving.
Beneath the banner of this purpose there is the insertion of "grace extending to more and more." Paul says that when people hear the gospel it results in thanksgiving. When more and more people hear the gospel it results in the increase of thanksgiving. This is the purpose for why Paul does what he does.
So then, some 1,955 years later, our thanksgiving for the gospel is fulfilling the Apostle Paul's ministry aim.
Today as we gather for Thanksgiving, let us gather in thanksgiving specifically for the grace that has been extended to us. And let us remember that our thanksgiving realizes the Apostle's goal, to the glory of God.