As is written in the psychology books, human behavior is like horseman and horse (conciseness and subconsciousness). The horse (subconsciousness) is making 95% of the decisions, and it is highly automated. In this way you don't need to think about every single thing and go crazy. Evolution made this so we function with ease.
But your conscious mind can change the subconsciousness decisions with focus. So when doing something important be highly focused, and don't do it all day long because you can't keep focus all the time.