What they really mean is, don't get demoralized. Don't think that you can't
do what other people can. And I agree you shouldn't underestimate your
potential. People who've done great things tend to seem as if they were a
race apart. And most biographies only exaggerate this illusion, partly due
to the worshipful attitude biographers inevitably sink into, and partly
because, knowing how the story ends, they can't help streamlining the plot
till it seems like the subject's life was a matter of destiny, the mere
unfolding of some innate genius. In fact I suspect if you had the sixteen
year old Shakespeare or Einstein in school with you, they'd seem impressive,
but not totally unlike your other friends.

Paul Graham
"What You'll Wish You'd Known" - http://www.paulgraham.com/hs.html