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.

Our educational system is not preparing people for the 21st Century. Failure is an essential part of entrepreneurship. If you work hard, you can get an 'A' pretty much guaranteed, but in entrepreneurship, that's not how it works.

Because startups often accidentally build something nobody wants, it doesn’t matter much if they do it on time and on budget. 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.

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.

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.

It doesn't matter if you call it a boom or a bubble. The startup business moves in cycles, and what goes up will eventually come down.

You know how people always talk about how vision is the key to entrepreneurship and perseverance and really seeing what other people don't see? We can actually redeem a fair amount of that folk wisdom.