We find in 2 Corinthians 10 that in Paul's absence there were those who spoke against his authority, and against him as a person. These attacks seem to have come only in his absence, not in his presence. Verses 8-10 shed light on the nature of the attacks:
“For even if I boast somewhat further about our authority, which the Lord gave for building you up and not for destroying you, I will not be put to shame, for I do not wish to seem as if I would terrify you by my letters. For they say, “His letters are weighty and strong, but his personal presence is unimpressive and his speech contemptible.” Let such a person consider this, that what we are in word by letters when absent, such persons we are also in deed when present.“
In order to counter the boastings and foolish claims of false teachers Paul engages in some foolishness of his own, as he describes. But when Paul boasts in 11:21-33 he boasts of the adversities he has faced, the tortures he has endured, the internal pain he feels. Paul is boasting in the way he says to boast in 10:17 “He who boasts is to boast in the Lord,” which is itself a quote from Jeremiah 9:23-24
“Thus says the Lord, “Let not a wise man boast of his wisdom, and let not the mighty man boast of his might, let not a rich man boast of his riches; but let him who boasts boast of this, that he understands and knows Me, that I am the Lord who exercises lovingkindness, justice and righteousness on earth; for I delight in these things,” declares the Lord.”
Paul presents to those who would deride him, and through him his message, an image of a man who has suffered greatly in this physical world both physically and emotionally. He presents unvarnished truth, framed in his great love for the church. He shifts the focus from himself, to the message he has carried and the one who gave him that message. Today we have Paul's boasting recorded as an example for us. Many people today identify as spiritual, but not religious, or as Christians, but not a part of a church. Reasons typically cited include the abuses of various religious organizations through the years, hypocrisy amongst Christians, or other reasons having more to do with people than the word of God. Christians need to take Paul's example and rise above the fray. If we boast, we must boast in the Lord. The emphasis must be on God's word, on Christ himself, not on us, the imperfect messengers. If we allow ourselves to receive top billing over the Lord, our efforts will undoubtedly fail.