George Will speculates on why Republicans are happier than Democrats. 

This finding is niftily self-reinforcing: It depresses liberals.

Will has two general conclusions: conservatives are happy because
they are pessimistic so when things don’t blow up it’s a good day, and
they’re happy because they pursue happiness. Progressives think of
happiness as a birthright that they deserve not as something active.
Their active pursuit is self-denial:

conscientious liberals cannot enjoy automobiles because there is global
warming to worry about, and the perils of corporate-driven consumerism
which is the handmaiden of bourgeoisie materialism.

Read it at Townhall