This from Wikipedia.
In the field of psychology, the Dunning–Kruger effect is a cognitive bias in which people of low ability have illusory superiority and mistakenly assess their cognitive ability as greater than it is. (...) Other investigations of the phenomenon, such as "Why People Fail to Recognize Their Own Incompetence", indicate that much incorrect self-assessment of competence derives from the person's ignorance of a given activity's standards of performance. Dunning and Kruger's research also indicates that training in a task, such as solving a logic puzzle, increases people's ability to accurately evaluate how good they are at it.
I have about 100 hours experience of hang gliding and a frankly embarrassing one hour in a 737 simulator. I know I can't fly an airliner.