If who thinks, that the smile is an indicator of happiness, I inform is not so. The smile is, more likely, a bait for happiness. I smile, that it, having lost vigilance, has flown during my life and remains in it. Anybody does not have affairs, that at the person inside if it gives away smiles the passer: and another's, malicious and kind, cheerful and sad. All are assured, that such person is happy.

If the girl of years of five, with a bow, in striped nosochkah by hops, and is unexpected so speaks: "Tyotenka, good to you of mood!", it is necessary to reflect. Something is not perfectly in order, and it is appreciable from the party. But only to children. Adults are too engaged in by the affairs, they in general see nothing around, except themselves. Perhaps certainly, not all. But many.
And the girl has told the mysterious phrase and has jumped further. Whence to it, small, it is known, that at me bad mood!? After all I go with hardly an appreciable smile on lips, I do not think at all about what, I consider green tiles in paved sidewalk. But there is it, and I having lost count, catching of that she KNOWS about my mood much more, than I. It is a paranoia?...

No, the happiness indicator is at all a smile. There is no indicator. The happiness simply is, then the girl silently passes by.