Smilling is beta

Smiling or laughing is an act of supplication. This is one of the ways chimps introduce themselves to a superior alpha chimp, btw (grinning or extending their palms to the alpha)

Similarly, notice how human alphas make a joke and everyone ELSE laughs. This is because the social interaction was dominated by the alpha and all the other humans then show their approval by laughing / smiling. In the old times if they didn't accept his dominance they would most likely just get their skull bashed in, so it is hard wired in human brains.

This is due to the fact that smiling is in itself a beta action.

Thats it. If this doesn't convince you to never smile, then you're a cuck