Well, I was the best student in my undergrad and then Master's program in theoretical physics. I received a number of local honor scholarships, and had a number of publications starting while I was an undergraduate student. I was assigned to teach grad classes when I was a grad myself. But I was sure that I am fraud. Too bad I did not know anything about the syndrome back then because I felt really bad. However at some point I figured what was causing me such pain - I just did not like physics, and did not want to do physics all my life. When I could admit that I dropped out from a grad school (PhD), and went to the industry meanwhile trying to figure it out what I would love to do. I figured that. And now I am banging the doors to my happiness - to attain a profession that is so interesting for me.
So... the question is - do you really want to do what you do right now?