The apostle Paul, as great as he was, was not without his periods of despondency.
When he penned First Corinthians, he informed the saints at Corinth that while he was with them, he experienced weakness, fear, and much trembling (1 Corinthians 2:3). This is very consistent with Luke’s narrative in the book of Acts.
While Paul was at Corinth, the Lord spoke to His apostle in a night-vision and admonished him: “Be not afraid, but speak and hold not your peace” (Acts 18:9).
In the Greek New Testament, the prohibition is literally: “Stop being afraid.” The implication clearly is that Paul was struggling with his spirit at this time, and the Savior came to his aid.
Underline the expression, “Be not afraid,” and in your margin note: Literally: Stop being afraid; cf. 1 Corinthians 2:3.
We must remember that God does not want the proclamation of His word to be characterized by a spirit of fearfulness (2 Timothy 1:7). You might, therefore, add this reference to your margin beside Acts 18:9 as well.