This is the lesson of Purim. It is for us to investigate into our own lives to see the miracles that have come into our lives. The truth is that all of our life is bound up with G-d's miracles. We are blind and callous to the true miracles around us. It is necessary for us to develop a spiritual sensitivity to appreciate the working of G-d.
Open miracles require no spiritual sensitivity, they require no effort on the part of man.
G-d does the work and man sits as a spectator at a football game. With hidden miracles, man must play the active role. This develops in him a spiritual side. He becomes aware of G-d in the world and in the every day events and in his own personal life. This is of crucial importance.