Optimism Vs. Realism
There is a psychological research finding that used a light switch as the variable. The experimenters had subjects flip the switch at will, and they varied the light on and off. It turns out that optimists were overconfident about their ability to control the elusive light, and depressed people were pretty accurate in how much control of the light they felt the switch actually had.
So, is the moral of this story that optimists might have less truth, but might be happier and more successful? How do you value truth vs. your own preferred version of reality? This can play a role in entrepreneurialism, but also of course the ability to gauge things like ARV, repair costs, silent costs, and potential speedbumps/pitfalls.