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.

If the plan is to see what happens, a team is guaranteed to succeed - at seeing what happens - but won't necessarily gain validated learning - If you cannot fail, you cannot learn.

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.

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.

The only way to win is to learn faster than anyone else.

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.

There was a study done in the early 20th century of all the entrepreneurs who entered the automobile industry around the same time as Henry Ford; there were something like 500 automotive companies that got funded, had the internal combustion engine, had the technology, and had the vision. Sixty percent of them folded within a couple of years.