Shi Fu, who dug the hole, was happier and more excited, so he got half drunk. Exactly: people are cheerful when they are happy, especially bright from the second month to the Mid-Autumn Festival.
Explanation: When people are happy, they are always full of vitality and spring breeze, just like the moon is always bright in the Mid-Autumn Festival.
When people meet happy events, their spirits are always particularly cheerful and exciting, just like when the moon comes in the Mid-Autumn Festival, it looks particularly clear. "People are refreshed when they are happy" is often used to describe people's triumphant demeanor when they are happy.