Paul Graham has written a tremendously insightful article analyzing great hackers. It is well worth a read whether you’re a hacker or not. Here are a few quotes:

• I’ve found that people who are great at something are not so much convinced of their own greatness as mystified at why everyone else seems so incompetent. The people I’ve met who do great work rarely think that they’re doing great work. They generally feel that they’re stupid and lazy, that their brain only works properly one day out of ten, and that it’s only a matter of time until they’re found out.
  
• When I think about the great hackers I know, one thing they have in common is the extreme difficulty of making them work on anything they don’t want to.
• Is there some quality that’s unique to hackers? I asked some friends, and the number one thing they mentioned was curiosity. I’d always supposed that all smart people were curious; that curiosity was simply the first derivative of knowledge. But apparently hackers are particularly curious, especially about how things work. That makes sense, because programs are in effect giant descriptions of how things work.

Note for the English-impaired: hacker does not mean someone that is attempting to breach security in this context.