Most phenomenal startup teams create businesses that ultimately fail. Why? They built something that nobody wanted.

This is one of the most important lessons of the scientific method: if you cannot fail, you cannot learn.

I would say, as an entrepreneur everything you do - every action you take in product development, in marketing, every conversation you have, everything you do - is an experiment. If you can conceptualize your work not as building features, not as launching campaigns, but as running experiments, you can get radically more done with less effort.

As an entrepreneur, I knew that if my company failed, I could always try again. So I often felt that the only real risk of true financial ruin came from the possibility of a serious illness that either exceeded my insurance plans lifetime limits, or was not covered due to rescission.

Except in very narrow cases, where there's breakthrough science that needs patent production, worrying about competitors is a waste of time. If you can't out iterate someone who is trying to copy you, you're toast anyway.

Sustainable growth is characterized by one simple rule: New customers come from the actions of past customers.

The goal of a startup is to figure out the right thing to build-the thing customers want and will pay for-as quickly as possible. In other words, the Lean Startup is a new way of looking at the development of innovative new products that emphasizes fast iteration and customer insight, a huge vision, and great ambition, all at the same time.