The fool says in his heart, “There is no God.” - Psalm 14:1

It is impossible for an athiest to live their life in complete radical devotion to the beliefs that they claim to hold.  The only way in which this could be made possible is for them to somehow revert into the state of nothingness that they claim everything came from.  This, of course, would cause an even greater dillema for them in the fact that they would then cease to exist.  Therefore they would no longer posess the ability to believe in anything at all.