It was for this very reason I left my corporate world job. I realized I was placing my future in the hands of those who thought they knew what I was capable of (supervisors, managers, etc.).
In September 2009, I finally realized only I know what I am capable of accomplishing, so I gave my 2 weeks notice.
It has been an incredible 5 year journey, but would not trade it for the security I had in that job. Whenever I wonder if I made the right decision, I go and have coffee with an old co-worker. When he begins talking about the same angry people and the same problems that existed when I left, I know the right decision was made.
Take a chance. Live a little.