Acts 18:9-10 - 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 you and harm you, because I have many people in this city.”
Fear can be a powerful thing. I've heard it described as False Evidence Appearing Real. Basically it is putting your focus and faith on a negative aspect of something. Then, when your focus is on that ‘fear’ it becomes larger in your mind than it actually is.
Take spiders for instance. Not many people particularly like spiders. They can bite, which is annoying and don’t get me started on their webs. Walking through those is less than desirable, but that is where it stops for me. Spiders are an annoyance, not a fear. I know I am bigger than they are and can kill them if necessary.
For some people, however, spiders are a terrifying thing. If they see a spider they will scream and run to get away from it. Even though they physically have the ability to smash and kill the spider, it has become huge in their mind and they are unable to function.
This is just one example of fear, but it can come in many different forms. Here in Paul’s situation we see him in prison, awaiting trial and for all he knew, death. It is apparent that he was getting discouraged. He had probably even thought about the fact that if he just conformed to what the leaders wanted he would probably be able to go free. He was maybe even questioning what he was doing as the fears rose inside of him. That is when God stepped in and spoke to him, “Do not be afraid.”
God has not given a spirit of fear, but of power, Love and a sound mind. When we keep our focus on God fear will not have an opportunity to sneak into our lives. If there is an area where you have fear take it to God and ask Him to show you the reality of the situation. When you have the truth of a situation, your fear will not seem nearly as scary.