Your hippocampus is the part of your brain that stores all your past successes and failures and the STORIES your brain has attached to them.
Every time an event happens in your life your brain reviews it as positive or negative BASED on the past experience that most closely correlates. In other words, you are always using the past to interpret the present.
So, if you want to conquer fears, you need to sit down and figure out what STORIES from your past no longer serve you. Then, rewrite them so you come out stronger and better.
So, for example, if you had a terrible experience speaking in front of the class in grade school and it now impacts your ability to speak to senior executives, you need to rewrite that story so you remove the fear from your brain.