Behind the door in the changing room at the pool is a neatly printed inscription: "I was having the worst day until you said Hi". The way the painter has gone round it rather than try to obliterate it makes it even more charming. I can't help smiling to myself.
After a good swim I walk down town and suddenly people in the street are smiling at me. I must be going around with a happy grin on my face and they respond. That makes me smile even more broadly. I've learned that the good feeling when someone smiles at us comes not just from their friendliness, which of course is nice, but from the effect of our own smile on ourselves.
Strange to think of that? It's a feedback loop, all about the vagus nerve which is the longest of the cranial nerves and forms a circuit linking the brain to the heart, lungs, diaphragm and gut. It's a major part of the parasympathetic nervous system which regulates heart rate, blood pressure, breathing and digestion and complements the sympathetic nervous system which is involved in the fight/flight system. Urban life gives too much emphasis to the sympathetic nervous system: when we run a red light, nearly get hit by a car on the pedestrian crossing, get angry at the boss's email or argue with our partner, even by text, the sympathetic nervous system acts as though a tiger has leapt out of the bushes. Often we stay cranked up all day.
The parasympathetic nervous system responds to calm and safety. This is where the smile comes in. The eye crinkles of a genuine smile signal to the brain that all is well. As the vagus nerve takes up the message, a cascade of subtle changes runs through our organs. Our system is calmed and regulated. Others can pick up the positive emotion and respond to it.
So 'smile and world smiles with you' plus you'll feel better for it . Just a gut feeling!