When I see people smile at me or even meet them smiling, I smile back as sign of respect and greetings. But you know what? I don't trust them at all. Why? People are great in fooling anyone. They will smile as if nothing terrible is happening to them. They will smile as if all is well, when actually deep inside, they are hurting, aching, enduring some pain. That's why I dont easily trust people when the smile but I smile back because Im no different from them. I also do the same thing.
Smile is the effective/best make up that a person can wear. It is something that you couldn't imagine or predict what reasons behind that make up. Any human is capable of faking their expressions by shwoing something relevant to make others feel at eased. But do you even know what truly smile is?