不亦乐乎 (bú yì lè hū): lit. isn't that a joy? (quote from Confucius); fig. (jocular) extremely; awfully

On Grandma's 80th birthday, more than thirty relatives came to the house. Mom was bustling around the kitchen with great delight, without even a moment to sit down and sip tea.

After retiring, Grandpa goes to the park every morning to play chess with old friends and practices calligraphy at home in the afternoon; his days are full and thoroughly enjoyable.

The children built sandcastles and collected shells on the beach, having a wonderful time, and only left reluctantly when the sun set.

To prepare for the school anniversary performance, the classmates rehearsed joyfully in the auditorium; although they were sweating from exhaustion, no one complained.