Statistically, a happy, naive child smiling 400 times a day is suppressed to a sophisticated adult of only 20 times, even though every adult knows that more smiling would be good to their own health. Are you a child or adult？ How many times do you smile a day？
I read the statistics on the SUN a moment ago. I am speculating the decaying may presumably follows an exponential law and the decaying time scale can be described using its half life that should be quite different among individuals.
no one smlie,smile represent kindness, weakness, warm–hearted. someone dare smiling, means their have these pensonalities, then others could easily bully them, or take advantage to them， stab them in their back