A radio program presented the idea of synchronicity.  The way that people automatically get in synch when they walk together is an example.  Synchronicity in fireflies was noticed and recorded in the 1500's.  Millions of fireflies would blink on and off in unison, lighting up the trees like Christmas lights.  One of the most interesting stories was of a heart patient.  He had a mechanical heart valve, which after several years was replaced by one of soft tissue.  He had become accustomed to the rhythmic clicking of the mechanical valve and the absence of the sensation caused him to suffer profound anxiety from the fear that the valve wasn't working and that he was dying even though there were no other symptoms.

The program was a reminder of the importance of the natural rhythms that we take for granted until they are disrupted.  It helps to explain our discomfort with change. [Russell]