From a chemical perspective, fear is an emotion the brain triggers when it recognizes a feared stimulus. A web of neurons is constantly processing and filtering information for what matters. This web can grow and change as we learn and experience new things. Like any learning the brain does, it requires some focus, some intention, and some repetition.

The answer depends on the source of the fear. In general, you probably have had things in your life you were scared to do, but you did them and then it was got a little bit easier. This is the simple idea behind overcoming fear. Small incremental steps and repetition.