If you "already know" it's very unlikely you'll put any effort into trying to understand some new or different way of solving a problem.
The illusion of knowing, is widespread in our society, even in the professions. Everyone tries very hard to protect their core beliefs. Denial is common.
Recognising that you were wrong, especially about something important, can be a deeply disturbing discovery. There might be years of uncertainty, and anguish to follow. It might take 10 years to regain one's confidence.
This is worksheet six of eleven. Collect the set.