The insidious voice that plagues a vision can be crippling. In his book, The Art of War, Steven Pressfield describes the lizard brain activity as the resistance. This resistance is always a voice in the back of our heads that wants to quit. It recoils from producing the good work we know our hand must release into the world.
There is no guarantee the world will respond with millions of followers or dollars, but learning to dance with the doubt, and still proceed, is where we will learn to crystallize the vision.
To complete another class, write another page, pitch another client, or compose another song is where the doubt is weakened. Incessant water drops will break a stone. Showing up to produce good work will shatter this stone of doubt and cripple the resistance. Climb to your feet and produce.