The ceremony is synonymous with happiness, but when it's associated with evil it becomes a negative phrase. There is also another way to look at this, we can also say that when we triumph over evil and celebrate the event, it's a sign of victory.
In the past many mythology, stories do mention the victory over evil and that's how we can relate to God as God is considered to be a superpower and has the ability to kill evil and come out of it.
This gives us a reason to celebrate festivals where we praise God for the effort and we worship God for its strength.