Yes, greet others with a smile!
Don't you know that smiling is making you attractive?
It's not just to change your bad mood, but it's take stress away from you also!
I ever heard that persons whom don't smile look much older, so please! keep your smile alive! It lifts your face and makes you look always younger!!
Here it is your smile! Don't you realize that you make you smile when you smile too?
Keep in your mind that people won't trust you or even like to talk to you if you don't show your teeth! :D
For all of those reasons, and more hidden benefits of a smile from you;
A Smile Is A Charity
So Keep Smiling!