When eating a little full, I like to hold my chin in my hand, but my mother won't let me, saying it's unlucky! But why? Who can explain, thank you.

Mainly due to the consideration of etiquette, such gestures and actions as pulling a bowl to eat (that is, eating without lifting a bowl), knocking on the bowl with chopsticks after eating, licking the bowl and so on. In the old society, he was regarded as a poor beggar. ...

This is to help you form good habits and have a civilized dining etiquette. It has little to do with Geely's bad luck.