Paul was afraid as he ministered in the city of Corinth. The reason we can believe this is because Jesus doesn't waste words. He comes to him in Acts 18 with an encouragement that addresses his fear.
It is a wonderful thing to have confidence if it is placed in the right source. Paul speaks about the secret he's learned to be content in any and all circumstances. He knows how to live in prosperity or in "humble means." What was the key to this contentment?