Start-ups make so many mistakes that the challenge to identify the root cause of a failure is tough. But believing in your own plan is probably the worst.

I believe for the first time in history, entrepreneurship is now a viable career.

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.

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

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.

If we stopped wasting people's time, what would they do with it?

Nowadays people talk about PayPal's founders as prescient geniuses who would inevitably change the world. It was, however, not so obvious that PayPal would taste its first major success by helping people sell Beanie Babies on eBay. But they had a vision, a hope, and the perseverance to try multiple iterations until they got it right.