I immediately thought about Tao when I read this and started smiling..... T.T ♥♥

(my translation)

"Do you know that only by seeing the laughs of the person you love some parts of your mind send a signal to take the smiling position unconsciously so you too smile even though you are in an inappropriate case. That's why the person you love's smile is considered as one of the most powerful reasons that can bring you happiness and joy immediately"  (trans by TaoRin)