One of the differenes between successful and unsuccessful startups is whether startup business model suits the founders personality.
Its one thing to be passionate about the idea and another to be able to build that idea into a sustainable model. If you are sensitive to cash flows and cannot bear the pressure, choosing a model where managing inventory or capital intensive infrastructure is core to the business can make you fail.
If you are uncomfortable with sales but the business model requires you to be sales focused can make it fail.
Ofcourse, there always comes a moment of truth and entrepreneurs do learn to cope with their personality weakness and can become successful.
Realizing what you are comfortable with or getting partners who compliment you helps in building a successful business