It is obvious that the various festivals are times of (happy), fun and excitement, not of sadness. They have many origins.
Some are (religion) and some are seasonal. Easter is an important festival for Christians all over the world. People are thankful because their food
(gather) for the winter and the agricultural work is over. Some festivals are held (honor) or satisfy and please the dead. In Japan a festival is called Obon. They have lamps on and play music they think this will help the dead back to Earth. The Dragon Boat Festival honors the famous ancient
(poem), Qu Yuan. Columbus Day is in memory the arrival of Columbus in the New World. India honors Mohandas Gandhi who helped gain India's independence from Britain. And most energetic and important festivals are the ones that look forward to the end of winter and to the (come) of spring, such as the Lunar New Year, on which people get together to eat, drink and have fun with each other.
No matter what the reason is, festivals are always times for great feasts with lots to eat, special and often new clothing to wear and (general) lots of fun.