I want to change the world.
Facebook, Sphero, Lytro, Zaarly, Meet up, SoJo
Time and the correlation between daunting hours of work and the rewards gained from that work. Entrepreneurship gives you the opportunity to grow. At the same time, that growth may receive very little or no positive feedback. Much of how success is viewed is contained within the eye of the beholder. As a person who views many things with a certain outlook of positivity, it can be very frustrating at times when it seems nothing has arisen from all of the hard work put into a project.
Unrealistic sales budgets. No matter how great a product may be it can only be implemented through expertise, capital and a burning desire to succeed!
1) Having the will to try-fail-try again.
2) Never be afraid of asking for advice or help. You can always learn from others.
3) Just go for it. When pursuing any endeavor it is important to be able to go through with it at the nth degree.