I use smileys though I feel a bit dumb when I do so :) All serious books are devoid of smileys. I'll keep the smileys. Here's Brain-Pickings on Saint-Exupery:
"Saint-Exupéry ends with a reflection on the sacred universality and life-giving force of that one simple gesture, the human smile: "Care granted to the sick, welcome offered to the banished, forgiveness itself are worth nothing without a smile enlightening the deed. We communicate in a smile beyond languages, classes, and parties. We are faithful members of the same church, you with your customs, I with mine." Four years after he wrote "Letter to a Hostage", (...) Saint-Exupéry disappeared over the Bay of Biscay never to return. Popular legend has it that Horst Rippert, the German fighter pilot who shot down the author's plane, broke down and wept upon hearing the news – Saint-Exupéry had been his favorite author. What a tragic form of contact, war."
If you ever wondered why Batman's The Joker cut his lips to make them look like a smile, the idea might stem from "Maldoror" by Le Comte de Lautréamont: "Seeing these exhibitions I've longed to laugh, with the rest, but that strange imitation was impossible. Taking a penknife with a sharp-edged blade, I slit the flesh at the points joining the lips. For an instant I believed my aim was achieved. I saw in a mirror the mouth ruined at my own will!" Now, why did Maldoror slit his lips? To fit in. Quite simply.
Without going this far, you can just plaster a smile on your face and, as studies have shown, it will make you happier. However, I suspect the best smiles emerge from truly happy individuals. But please, keep smiling anyways :) Actually, I find smiles evolutionary interesting. In itself, it's an effort to flex cheek muscles rather than not, so why do we do it?
Dennett in "Intuition pumps" gives the example of Gazelles' strange habit of stotting - jumping extremely high - when predators pursue them, despite it making them lose speed. But it's actually to signal they are the fittest and so to assure the predator he has no chance of catching them. Same for smiling! An application? Well, in clubs of course :) The most interesting people are the ones smiling. It signals fitness doesn't it? Good morning Impossible Family ;)