Doing and achieving goals is the only way to really prove what you can do, getting started is the best way to overcome what you fear and think its not possible, I've gone through that when you stop talking about what you want to do and start doing it, even if you fail but what is the best leason if not failure, then you start getting closer to your goals and once you see that something works, it's much easier to stop worrying about what other people think because even when things go wrong you end up learning something.