I can see both sides on this one, you should certainly be self-aware enough that you periodically reflect deeply; I think the danger is that far too many guys in their 20s get into a rut, paralysed into inaction through over-analysis; your 20s and 30s are the time you should be vigorous, active, taking risks, exploring, having experiences, and doing so will result in more self-knowledge than sitting in your room contemplating the universe. In general, it's better to err on the side of action - when in doubt, build something.