In my efforts as a serial entrepreneur and a doctoral student in executive leadership, I have found that the feelings of fraud come from multiple sources such as: ethical considerations; no validation on tactics, strategies, or in leadership; and the loss of focus on market segments. The secret of success in entrepreneurship and in all of the other areas of life is five-fold:

Believe in yourself, your team, your product, and your direction;
Adjust to changes in your environment for yourself and then your team;
Immerse yourself all the way in to what you are doing;
Connect with your heart in the decisions made for validation of belief; and
Endurance through self conditioning for success.