He just expects mastery and perfection at the get-go.
This has been our experience with our DD14. She's always been like this. It's not exactly correlated with her level of interest, ability, or desire for mastery, either.
Nor is it wholly rational, as phey noted with her DS.
Having explored what she DID mean about such statements, it appears that in her case, what she means is that she has some standard (often "100%" in graded/evaluated performance/activities) and anything less than that is "not great." Couple with a sense that she has not got any 'stand out' abilities (and, er-- she doesn't-- but only because she is SO good at SO many domains), and she interprets all of her very real ability as "nothing special," and feels that she doesn't have anything in particular to take pride in.
I don't know that one CAN truly combat that view of the self. Because on some level it is true-- that the person feeling that way doesn't have an (meaning singular) area of "strength" to reflect upon in comparison to other areas which are weaknesses.
It would seem as though external validation would be a route to countermanding this, but we've found that is not really so, because the expectations and standards imposed are ever-escalating.
For an example of what I mean:
last year, my DD won a state championship ribbon for an apiculture poster, and a reserve (second place) in general educational displays for one on a 'dog' topic. She also won county championships in not just those two areas, but in FOUR others. Remember, she's 3-4 years younger than peers/competitors.
So this year, having been grade-skipped-- AGAIN-- and now being a full 4 years younger than most of those competitors, plus having a more-than-full-time job as a result of a high-level summer internship in a research lab... she still won a state championship and a reserve. In the next age division up (senior division-- 11th-12th graders).
I mention this because she was HORRIFIED and disgusted with herself at this outcome. Is that crazy or what?
But that's a perfectionist for you.
She also has this (irrational) sense that "everyone" expects her to come in 1st place all the time... and, uhhhh-- ABSOLUTELY NOT. She's not getting that from ANY of the adults in her life. Not a bit. Nor is she getting it from friends, so far as I can tell. Now that is a socially-prescribed perfectionist for you.
She self-handicaps, she avoids possible failure, and she procrastinates. All because of this quirk of thinking.