The French Revolution lasted ten years, but for many people 1793-1794 was the worst. One politician said, "Let's make terror the order of the day!" During this "Reign of Terror," it is believed that 300,000 people were arrested, 17,000 were executed, and 10,000 died in prison.
When Paul called on Christians to "persuade men" because we know "the TERROR of the Lord," this was not the kind of terror he was talking about. Other versions translate this as "the FEAR of the Lord." To fear God is to have respect and reverence for Him, to understand He is holy, just, and righteous, and to learn how much He hates sin. This fear includes a strong desire to not displease the Lord.
To gain this healthy "fear of the Lord" requires getting into God's Word (Bible reading and study). Psalm 119:38 promises that God's Word (when proved and confirmed) produces fear (or reverence for God).
Proverbs 2:1-5 has great instructions for understanding fear and finding Godly knowledge. Verse 1 - RECEIVE God's words Verse 2 - APPLY your heart to understanding Verse 3 - CRY after knowledge Verse 4 - SEARCH for knowledge and understanding Verse 5 - "THEN shalt thou understand the fear of the Lord, and find the knowledge of God."
It is dangerous to be a Christian (a "salesman" for Christ) and have little real fear (reverence, understanding, and knowledge) of the Lord. "We fear men so much because we fear God so little" (William Gurnall).