The Washington Post has this article on the relative happiness of liberals and conservatives. Grover Norquist is quoted and he is, indeed, always a chipper fellow. I have seen these polls before and it does seem that conservatives are tempermentally more cheerful than liberals. I'm not but I do recognize the phenomenon.
What once was said about Puritans can be said about liberals, they are all beset by the paralyzing fear that someone somewhere is enjoying himself (and voting Republican).