Now this relaxation of the mind from work consists on playful words or deeds. Therefore it becomes a wise and virtuous man to have recourse to such things at times.

One's age should be tranquil as childhood should be playful. Hard work at either extremity of life seems out of place. At midday the sun may burn and men labor under it but the morning and evening should be alike calm and cheerful.

Humor is the instinct for taking pain playfully.

It's sort of a mental attitude about critical thinking and curiosity. It's about mindset of looking at the world in a playful and curious and creative way.