By simply turning his focus to one side, he would have easily exited his prison. Rather, due to his intent on one direction, he remained confined, captive.
Don't let one success keep you from pressing on to bigger and better things. Constantly set new goals, and you will attain things you never dreamed were possible.
I am that stranger who has nothing to give you and who is telling you to look inside. Not inside any box, as in the parable, but somewhere even closer: inside yourself.