The cost of consistently letting your fears drown out your desires is that you sacrifice your life to negative outcomes that exist only in your mind. The fact is, most of the worst of what we fear never comes to pass.
Often, the risk of listening to our fears is greater than the risk of the negative outcomes we imagine. This is because we let our fears deny us of opportunities that could ultimately be life-changing if only we had the courage to do what we truly desired. And even if what we feared came to pass as a result of our initiative, the outcome is simply temporary discomfort (embarrassment, rejection, criticism…) and insignificant in the grand scheme of our lives.