Incompetent people lack the expertise to recognize that they are incompetent. We can observe this in other people, but it is very hard to see it in one self. We might think we are doing great at something, while in fact be doing it quite poorly.
According to Adam and David, only by realizing that you are not good at something will you be able to ask question and improve, in order to get better. It's the people who have no awareness of how poorly they are performing are the people who will not improve.
You become the master of something the day you realize that you have to be a life-long student of it.
When starting to work on anything, most people start appropriately uncomfortable, unsure of what they don't know. This helps beginners to pay close attention and avoid mistakes. But with a little knowledge under their belt, their confidence explodes to the point where they think they know what to do, but they don't actually know, and that's where the mistakes start to seep through.