A colleague told me that when her 7-year old daughter is grumpy or mad, she asks her to give mummy a smile, and repeats this request very friendly until the daughter produces a strained smile. The mother will continue to ask for “a real smile!”, and at that point the daughter usually relaxes and gives her a proper smile – and the annoyance is gone.
That’s just what it is about: when you smile you relax the muscles in your face and this relaxation normally spreads down to your shoulders and belly. The tension of irritation or bad temper is released and you actually feel better.
Of course you don’t need a mother to tell you to smile: whenever you feel negativity creeping in upon you, tell yourself to smile. At first it may just be strained, but if you continue you’ll be able to make it a real smile – and you will immediately feel better!