"I love my three young children immensely. So it's hard for me to be fully rational about them. Of course they are the smartest, the best looking, and the most athletic. I'm not alone — all parents are irrational."

"Irrationality can be a strong asset. Sure, a vast majority of new businesses fail, so a fairly rational person could easily justify maintaining the status quo. But our world is — unquestionably — a better place because people take risks that don't quite make logical sense. Of course, irrationality presents challenges too. It can blind innovators to real problems and to important signals telling them to do something different. Yes, perseverance may be an underappreciated skill, but when paired with passion, it often leads to fanaticism.

So how can you toe the line between irrationality and fanaticism without pursuing a doomed idea?"