It is impossible for a man to learn what he thinks he already knows.

Assumed knowledge is the most effective barrier there is, because it removes the sense that there is anything to look at. You cannot pay attention to something already filed as understood, and the filing usually happened years ago on the basis of one explanation. This is why experienced people are often the last to learn a change in their own field.

Pick something you would say you know well and find out how it is done now, or ask someone who does it differently to walk you through their version. The aim is not humility as a virtue. It is to find out where your understanding stopped updating.