2Cor 12:16-19 Be that as it may, I have not been a burden to you. Yet, crafty fellow that I am, I caught you by trickery! Did I exploit you through any of the men I sent you? I urged Titus to go to you and I sent our brother with him. Titus did not exploit you, did he? Did we not act in the same spirit and follow the same course? Have you been thinking all along that we have been defending ourselves to you? We have been speaking in the sight of God as those in Christ; and everything we do, dear friends, is for your strengthening.
Paul was rather annoyed at the fact that he had to defend himself, given his credentials, the miracles he had performed in their presence and the sacrifices he made on their behalf. And thus the facetious rhetoric he's been using. Here he's making fun of the fact that his enemies are being crafty, while here he speaks facetiously of being crafty in that he proved his sincerity in just the opposite way of his enemies, who likely demanded pay for their ministry. To the Thessalonians he wrote, "You know we never used flattery, nor did we put on a mask to cover up greed— God is our witness. We were not looking for praise from men, not from you or anyone else. As apostles of Christ we could have been a burden to you, but we were gentle among you, like a mother caring for her little children." 1Thess 2:5-7 Likewise Titus followed the same example. Ministers who sacrifice personal rights and entitlements gain credibility.
Just as parents should look to the edification of their children, despite the personal sacrifice it may require of themselves, so also children should recognize and appreciate such sacrifices that were made on their behalf.