Do you need more RHATHYMIA in your life?

What's the word I'm thinking of? Today, it's.... 

RHATHYMIA [ruh-THY-mia] (noun)

Light-hearted, carefree behavior

"The Beatles proved that one could combine rhathymia with mayhem in ‘Maxwell’s Silver Hammer,’ their bizarrely jaunty little ditty about a serial killer." (TWITO, page 125)