from Grothendieck's Récoltes et Semailles:

    In those critical years I learned how to be alone. [But even] this
    formulation doesn’t really capture my meaning. I didn’t, in any
    literal sense, learn to be alone, for the simple reason that this
    knowledge had never been unlearned during my childhood. It is a basic
    capacity in all of us from the day of our birth. However these three
    years of work in isolation [1945-1948], when I was thrown onto my own
    resources, following guidelines which I myself had spontaneously
    invented, instilled in me a strong degree of confidence, unassuming
    yet enduring in my ability to do mathematics, which owes nothing to
    any consensus or to the fashions which pass as law. By this I mean
    to say: to reach out in my own way to the things I wished to learn,
    rather than relying on the notions of the consensus, overt or tacit,
    coming from a more or less extended clan of which I found myself a
    member, or which for any other reason laid claim to be taken as an
    authority. This silent consensus had informed me both at the lycee
    and at the university, that one shouldn’t bother worrying about
    what was really meant when using a term like “volume” which
    was “obviously self-evident”, “generally known,” “in
    problematic” etc... it is in this gesture of ”going beyond to be
    in oneself rather than the pawn of a consensus, the refusal to stay
    within a rigid circle that others have drawn around one -- it is in
    this solitary act that one finds true creativity. All others things
    follow as a matter of course.

    Since then I’ve had the chance in the world of mathematics that
    bid me welcome, to meet quite a number of people, both among my
    “elders” and among young people in my general age group who were
    more brilliant, much more ‘gifted’ than I was. I admired the
    facility with which they picked up, as if at play, new ideas, juggling
    them as if familiar with them from the cradle -- while for myself I
    felt clumsy, even oafish, wandering painfully up an arduous track,
    like a dumb ox faced with an amorphous mountain of things I had to
    learn (so I was assured) things I felt incapable of understanding
    the essentials or following through to the end. Indeed, there was
    little about me that identified the kind of bright student who wins
    at prestigious competitions or assimilates almost by sleight of hand,
    the most forbidding subjects.

    In fact, most of these comrades who I gauged to be more brilliant
    than I have gone on to become distinguished mathematicians. Still
    from the perspective of thirty or thirty five years, I can state
    that their imprint upon the mathematics of our time has not been
    very profound. They’ve done all things, often beautiful things in
    a context that was already set out before them, which they had no
    inclination to disturb. Without being aware of it, they’ve remained
    prisoners of those invisible and despotic circles which delimit the
    universe of a certain milieu in a given era. To have broken these
    bounds they would have to rediscover in themselves that capability
    which was their birthright, as it was mine: The capacity to be alone.