2 Corinthians 12: Thorn in the Flesh

The Corinthians respected the "super apostles" so much that they paid money (salary?) to them while Paul restrained himself and he didn't charge anything from them. Paul was interested in the hearts of the Corinthians, not their money. Paul was thinking about what made the Corinthians pay so much attention to the super apostles and he begins to brag about spectacular revelations from the Lord, but then, he stops because he understands that:

7-10 Because of the extravagance of those revelations, and so I wouldn’t get a big head, I was given the gift of a handicap to keep me in constant touch with my limitations (the thorn in the flesh). Satan’s angel did his best to get me down; what he in fact did was push me to my knees. No danger then of walking around high and mighty! At first I didn’t think of it as a gift, and begged God to remove it. Three times I did that, and then he told me,
My grace is enough; it’s all you need.
My strength comes into its own in your weakness.

Paul had a thorn in the flesh, a suffering, but he realizes that this suffering made him seek and pray to the Lord. Instead of bragging about his intelligence, etc.; Paul brags about his sufferings because they made him more dependent of the Lord. For Paul, a great man is the one who depends on the Lord.

2 Corinthians 11: Paul is jelous of the "super apostles".

Paul is jealous of the "attention" that the Corinthians were giving to the "super apostles" because Paul understood that they were being mislead and used by them. It is similar to a woman that always fall in love for the wrong guy and can't see who really takes care of her. Paul decided to show that he is fully compromised with Jesus. How? Instead of showing how Jew he is, his education, etc; he showed them how he had hard times because of Jesus: he was flogged, beaten Roman rods and even betrayed by people form the church.
This makes me wonder that a Christian life is not about being elevated by the Lord above others; it is all about being identified with Jesus. 

2 Corinthians 10: Misjudgement

Imagine a father that sees his child as fool: instead of valuing his father's care, the child longs for bad companions. Paul is in a very similar situation. Many in Corinth value others with much more charisma than Paul. They have their arguments against Paul. Paul says to the Corinth church:

3-6 The world is unprincipled. It’s dog-eat-dog out there! The world doesn’t fight fair. But we don’t live or fight our battles that way—never have and never will. The tools of our trade aren’t for marketing or manipulation, but they are for demolishing that entire massively corrupt culture. We use our powerful God-tools for smashing warped philosophies, tearing down barriers erected against the truth of God, fitting every loose thought and emotion and impulse into the structure of life shaped by Christ. Our tools are ready at hand for clearing the ground of every obstruction and building lives of obedience into maturity.

In another version we read:

5 we are taking every thought captive to the obedience of Christ.

Paul enemies had their thoughts which would separate the Corinth church from the Lord but that was very obscure. Paul wanted to clarify every though and bring into the structure of life shaped by Christ. For instance: the enemies of Paul were used to commend themselves but:

18 For it is not the one who commends himself that is approved, but the one whom the Lord commends.

2 Corinthians 9: Generosity

I have been stingy, mainly due to my hardships in childhood. I was told to save for the rainy days over and over, so I have been saving even now. I realize that this thought has a problem: it prevents me from being generous because in its essence I wrongly have been believed that I depend on my effort, my work and in the rainy days I will be alone: no one will be there to help me.

Paul wants that the Corinthians help the church in Jerusalem. He argues that the Lord has been good to them, so that they may be good to others. He expects that the Corinthians be joyful when being generous. The future is in the Lord's hand and the Lord is the One who provides, so the one who believes in the Lord is free to give. Paul expects that the Corinthians help the Jerusalem church and in doing so, they will be blessed by the Jerusalem church. It is difficult to live in community without generosity.

2 Corinthians 8: Gentile Offerings to Jerusalem

One year before, the Corinthians had a plan to offer money to the church of Jerusalem; but this plan wasn't being conducted and Paul had to revive it. One argument is that communion means to help one other falls and vice-versa:

10-20 So here’s what I think: The best thing you can do right now is to finish what you started last year and not let those good intentions grow stale. Your heart’s been in the right place all along. You’ve got what it takes to finish it up, so go to it. Once the commitment is clear, you do what you can, not what you can’t. The heart regulates the hands. This isn’t so others can take it easy while you sweat it out. No, you’re shoulder to shoulder with them all the way, your surplus matching their deficit, their surplus matching your deficit. In the end you come out even. As it is written,
Nothing left over to the one with the most,
Nothing lacking to the one with the least.

Paul explained how the offerings should be collected and how Titus and other two friends would take care of it. In fact, we understand that Paul and others carried the offering to Jerusalem and delivered it to leaders of the church in Jerusalem around Acts 21. Paul was always eager to see Jews and gentiles united due to the Messiah's sacrifice.

2 Corinthians 7 Metanoia

Paul wrote an angry letter to the Corinthians showing their sins before "2 Corinthians". Paul was worried about how they would read his letter: "perhaps they would be grieved and offended". Titus brought news to Paul about how his letter was received. It produced "metanoia", a new view about their sins, a repentance that made them confess and hate their sins.
Paul became very glad about their reaction;

11-13 And now, isn’t it wonderful all the ways in which this distress has goaded you closer to God? You’re more alive, more concerned, more sensitive, more reverent, more human, more passionate, more responsible. Looked at from any angle, you’ve come out of this with purity of heart. And that is what I was hoping for in the first place when I wrote the letter. My primary concern was not for the one who did the wrong or even the one wronged, but for you—that you would realize and act upon the deep, deep ties between us before God. That’s what happened—and we felt just great.

2 Corinthians 6 - Misunderstood by others

Perhaps I am a little different than "normal" Brazilians; and it is common that I feel to be misunderstood.  Today, I was looking the sky and I thought: the Lord is One who can't misunderstand me; maybe it is common that I don't understand the love and patience of the Lord, that I misunderstand the Lord, but the Lord is gracious and always understand me.
Reading 2 Corinthians 6, Paul was misunderstood by others. He showed love to the Corinthians, but they didn't understand Paul. Paul wrote:

11 Oh, my dear Corinthian friends! I have told you all my feelings; I love you with all my heart. 12 Any coldness still between us is not because of any lack of love on my part but because your love is too small and does not reach out to me and draw me in. 13 I am talking to you now as if you truly were my very own children. Open your hearts to us! Return our love!

However, Paul knows that the Lord understand him:

9 The world ignores us, but we are known to God; we live close to death, but here we are, still very much alive. We have been injured but kept from death. 10 Our hearts ache, but at the same time we have the joy of the Lord. We are poor, but we give rich spiritual gifts to others. We own nothing, and yet we enjoy everything.

Paul taught me a lesson that I would like to live: to know that the Lord understands me and appreciate that.