Humbleness

Edsger Dijkstra: The people who are best at programming are the people who realize how small their brains are. They are humble. (via Coding Horror).

Be humble. Even if you're smart as hell, follow a set of simple practices (unit-test, small methods, refactor mercilessly, proper naming of functions/variables/constants, ...). Now you're in a position to put your brain to good use on those hard problems which inevitably come up while coding.