People who succeed in life are people who take risks. Many rich people often lose large fortunes on the chances that they take, but they keep going because the next risk may pay off. If you continually listen to your amygdala or "lizard brain" you cannot be successful because you will also give in to your fear.
Instinct tells us to run and flee from risk. We are programmed to fight change and run away from challenges.
These reactions are so deep in our programming that they are not going to change overnight, but they can be changed. It also won't be easy but it can be done.
You reprogram the amygdala a little bit every time you conquer your fear. You don't want it to go away completely, we still need it for those times when we really are in danger. But we need to listen to it only when needed, when we face real danger.
That is when we will truly find success.