I am trying to find Paul Graham's essay that mentions something to the effect of "hackers can't know if they're good". In it, he says he (with a seemingly false humility) says he himself doesn't even know if he's good.
P.S. Sorry for the softball question. I did try searching his site and it was unproductive.
http://www.paulgraham.com/gh.html
Economically, this is a fact of the greatest importance, because it means you don't have to pay great hackers anything like what they're worth. A great programmer might be ten or a hundred times as productive as an ordinary one, but he'll consider himself lucky to get paid three times as much. As I'll explain later, this is partly because great hackers don't know how good they are.
http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect
The Dunning-Kruger effect makes interesting reading, too:
The Dunning–Kruger effect is a cognitive bias in which "people reach erroneous conclusions and make unfortunate choices but their incompetence robs them of the metacognitive ability to realize it"
Is this it? http://www.paulgraham.com/gh.html
Oops I was a bit slow :)