Paul was bold in speaking because the Lord kept on reminding him that there were many others walking with the Lord. Remember you are not alone. The Lord is with you, and there are other followers of Jesus who are also being strong in the Lord.
One night the Lord spoke to Paul in a vision: “Do not be afraid; keep on speaking, do not be silent. For I am with you, and no one is going to attack and harm you, because I have many people in this city.”