KEEP THOSE HANDS UP

Don't confuse yourself with a professional fighter.  Yes, aspire to be like that, but you keep those hands up and you keep yourself protected unless its part of your strategy to force them take that shot using your attack by draw principle.  Also, out in the real world you need those hands up as there might be more than one opponent and you don't want to get blind sided.  The typical Krav Maga stance has the fists clenched and up at either side of the face protecting the jaw line.  The legs can defend the low line and the hands can look after the head and torso.  Just think about holding and big old phone up at your head.