My hypothesis has for years been that this entire construct develops as a result of a child never really experiencing ABJECT failure... at anything.
My DD is just plain way too good at almost everything she tries. To the point that she expects instant success, and interprets the lack of it as failure or weak skills/ability.
Her version of the "success to failure" continuum is compressed, basically, into a range that most normal people would think of as being about 80% to 100+%. In her mind, 80% is "awful. Clearly I should go home and never do this again because it is obvious that I have no innate talent TO develop in this activity."
We have to engineer and force failures on her in an effort to break through that awful glass wall that she's built around this. I'm sad to say that these things make us feel terrible as parents-- and even worse when they backfire and she hits something out of the park ANYWAY in spite of almost certain failure. Well. I say "out of the park" when I mean "above average relative to others older than herself who have invested serious amounts of time and energy in getting to some level of proficiency."