HERE is an obvious personal flavor here in this chapter. Paul had not visited the Corinthians as he had intended, so he defends that choice here. Basically, he had waited to go see them because he wanted to give them more time to get themselves together. He knew that as an apostle, when he arrived, he would be obligated to judge the unruly members in that church (vs. 23).
Seeing that Paul had genuinely kind and generous feelings toward the Corinthians, he was concerned about their suffering, & desirous in their relief. Of course, Paul knew very well what it felt like to suffer. More precisely, Paul had suffered much as a direct result of his faith in Jesus Christ. But, he had also experienced God's comfort. He knew what it was like to receive a special dose of God's magnanimous grace during difficult circumstances. There had been times when Paul had wished for death (vs. 8). But Paul didn't live his life in his own strength. He had learned to trust God in all situations.
Since Paul had endured much pain, as he gave advice and offered consolation to others in pain, he had a voice worth heeding; a firm platform to stand on. He begins by reminding us that God is an incomparable source of mercy & comfort (vs. 3). Then he adds that the tribulations & troubles (which we all suffer) serve as opportunities for God to strengthen & comfort us (vs. 4-5). We then, in turn, are equipped to sympathize with others. We become conduits of God's comforting kindness. Having been there, we can care, & our care is believable (vs. 6).