Being afraid in a dream is usually a sign that something is frightening you in waking life.
Dreams usually use symbols to represent abstract ideas, so if you are frightened of a person, an animal or an object in your dream, you could really be afraid of something much more abstract, such as a memory, an emotion, a belief or a change in your life.
It is possible that you are not acknowledging your fear, which is why your fear is revealing itself to you in your dream.
You may have been procrastinating or avoiding dealing with something, telling yourself that you have other, more important things to do.
Your dream is telling you to acknowledge your fear and then face it.