The third wall: physiology
The most restricting wall of the box, and the one that has the greatest effect when it is pushed out, is the physiology wall – our inability to make use of the capacity of our brains. Moving our thought processes out to the extremities, at one extreme (almost) unconscious daydreaming and at the other focused flow, are two ways of increasing the connections in the brain and making better use of the physiological potential of one's brain.
Take a handful of coins (if your have no coins, then buttons, raisins or whatever is at hand will do just as well). Throw them onto the table. Look at them for two seconds and then close your eyes. How many were there?
You probably failed at this counting exercise. If you succeeded, it was probably because there were far too few coins/buttons/raisins or whatever it was you threw onto the table. If there were five or less, then the problem is too easy. If you threw down more than five coins/buttons/raisins and managed to count them, then you are to be congratulated on being one of a minute fraction of the world population who are blessed with unusually good physiology in the form of a slightly more hard-working brain.
This simple exercise tests your ability to use both halves of your brain simultaneously. The left half of the brain can count, but only up to seven plus or minus two units at a time. The right half of ...