Unskilled and Unaware of It
Justin Kruger & David Dunning · 1999
"People with low competence in a domain tend to overestimate their own ability, because the same skills required to perform well in that domain are also the skills required to accurately judge good performance — so incompetence doubly disadvantages you: it produces poor results and simultaneously removes your ability to recognize that the results are poor."
Kruger and Dunning tested this across several domains, logical reasoning, grammar, humor, and found a consistent pattern: participants who scored in the bottom quartile on actual tests dramatically overestimated their own performance and ranking relative to peers, while top performers, if anything, slightly underestimated their relative standing, since they assumed tasks that felt easy to them were probably easy for others too.
Read more about the topic
The Psychology of Sunk Cost
"People irrationally continue investing time, money, or effort into a failing course of action specifically because of what they've already invested — even though that past investment is gone regardless of what they do next, and only future costs and benefits should matter to the decision."