Note 3 at 1 Cor. 2:3: Paul seems to be describing a self that is completely inconsistent with the impression that his actions give and that he promotes in his own teaching. However, there is no contradiction. He is simply describing how he felt in his flesh (see note 3 at Rom. 7:18, p. 790).

He had negative feelings and emotions, but he didn't let them dominate him. Instead, he walked in the reality of who he was in the spirit. The end result was that in his actions he was not weak, fearful, or trembling. But this wasn't because he didn't feel these things. He had learned to not live according to his own feelings but to let Christ live through him (Gal. 2:20).

The reason he describes his natural feelings is to remind the Corinthians that he didn't rely on himself when he ministered to them. If he had, they would not have seen the supernatural confirmation of the power of God that he describes in the next verse. Therefore, they shouldn't reject his instruction because it wasn't him that was speaking, but God speaking through Paul.