My answer: I'm not good at dealing with people. When I'm talking about mathematics or computer science, I'll argue with people without giving a moment's thought to who I might antagonize, because at that point I'm dealing with the subject and not with the people. In social contexts, by contrast, I can't avoid the human factor, and I back away from anything which could potentially result in a confrontation. I think holding my ground when I know I'm right is a good thing; but I'm working on being less of a wimp in social situations.
It really doesn't matter what you say here, as long as you say something coherent. The point of the question isn't to find out your opinions of yourself; rather, it's to determine your level of self-awareness. Saying "I have problems X, Y, and Z" shows far more self-awareness and will win you more points than reciting a list of your accomplishments.