I've discovered a great new method of growing bigger ears. Ready? Wait for it... go listen to sales pitches from startup consultants.
If you're an entrepreneur, then you probably don't like being bossed around and you might think your own opinion is pretty damn good. If you didn't, you probably wouldn't be starting your own company.
(I'll admit it, I have both of those flaws to varying degrees.)
Given those two features, you may or may not have a tough time (like me) really shutting up and listening to your customers. It's always tempting to interject your own opinion, and even if you think you're just asking a clarifying question, you're probably adding some spin to it to try to nudge your customer's responses the way you want...the way you expect...the way you know your customers ought to be thinking.
But if you do that, you're not getting real customer feedback. Instead, you're just stroking your own ego and validating an opinion rather than validating a hypothesis.