People generally do not like confrontation and will go out of their way to compliment you even when you have totally screwed up. The easiest place to catch yourself doing this is after a mediocre meal. I’ll too easily let the owner know “it was great” when in fact the meal was a barely edible.
It is critical to be honest with yourself, how you run things, and the product you push out to customers. Whether it is software, physical goods, or a service, never blow smoke up your own ass. Listen to the negatives. You know where most of the rough edges are, which ones to keep and which ones to round out. But there are hidden ones, which is why secret diners are such a great way for restaurants to truly get to the problems they never knew existed.
It is hard to learn form the positives. One, because you accomplished something you already knew. But more importantly, you will actually be paying attention when a negative is brought to your attention.
People who are openly negative are rare, but honest. Listen and determine whether action is required or not.