Be pretty if you are,
Be witty if you can,
But be cheerful if it kills you.
If you're so evil, eat this kitten!
The Wikipedia article is pretty decent. Originally written in 1840 or so as part of a response to someone who was writing a book on Illinois history or something and wanted information for include a chapter on Mormons. The fellow didn't end up using the information in his book but it's still a pretty good capsule description of the gospel. I might loosely paraphrase it thusly in my own idiom: