Impostor/fraud syndrome is quite common amongst quite a few founders I know. I personally believe it's just a cognitive deficiency one has to overcome. As long as it doesn't get in your way, it's OK.

Truth of the matter is, you're not entirely responsible for all of your successes. Time, space, opportunity and many other factors far beyond our control are always necessary.

However, lack of success does not mean you have nothing valuable to contribute. Most "successful" entrepreneurs often attribute their success to "Luck" & hard work. the hard work part is something you can definitely speak to regardless of how the luck part went for you.

Reference: http://en.wikipedia.org/wiki/Impostor_syndrome