All I can tell you really is if you get to the point where someone is telling you that you are not great or not good enough, just follow your heart and don't let anybody crush your dream.
“We are at the very beginning of time for the human race. It is not unreasonable that we grapple with problems. But there are tens of thousands of years in the future. Our responsibility is to do what we can, learn what we can, improve the solutions, and pass them on.”