I am a Cap.
Let's see.. what drives me? Myself.
I truly believe one should decide for themselves what to do, how to think, how to be and so on.
Never let the herd influence your actions. I'm not one for trends. Just because something is deemed cool does not mean it has to be mine.
What challenges me? Motivation and procrastination.
Despite everything you've read about the Capricorn, lack of motivation is my biggest pitfall. Its really the GETTING motivated that is the issue because once I've decided I want or need to do something I'm a force to be reckoned with.