Chapter 24 of Thinking, Fast and Slow is called "The Engine of Capitalism." It is, of course, about irrational optimism. But that's not the only type of bias which afflects entrepreneurs. One of the others is "competition neglect." We become so focused on the originality of our ideas, we forget that we have competition, and they are moving in on customers at the same time as we are.
As a way of preventing ourselves from losing track of the competition, we can make it a practice to gather ideas from them on a regular basis. Talking with customers is wonderful, but talking to the competition is so much more exciting! Even if you don't share James Altucher's desire to take them to lunch, you should always be studying them, collecting as much information from them as you do from your customers.