Yeah mate I dont know how, but even when your faced with something that could kill you and fight or flight reflexes are about to set in ,if you smile your brain catches on and follows the lead slightly and does something in reverse up the same nuron path and you relax a bit.

When you think about it that may or may not be so good in some situations.


In other situations like being threatend on the street it is an advantage because it puts a question into the attackers mind that you could be a nut and he has picked on the wrong person, (in which case he would be correct) .