Humour is one of those things that you recognise about the time it makes you smile. Most people would rather enjoy it than figure out its rhetorical secrets. But there’s good reason to make an effort: not everyone is born a humorist, and I believe that those of us left without the gift can still learn to throw a joke, the way even the worst apprentice learns to throw a pot—it may be a laughing stock, but it’ll hold water.
Don’t let the first line of the Quote throw you.
Quote: Practically everyone is a manic depressive of sorts, with his moments and his down moments, and you certainly don’t have to be a humorist to taste the sadness of situation and mood. But there is often a rather fine line between laughing and crying, and if a humorous piece of writing brings a person to the point where his emotional responses are untrustworthy and seem likely to break over into the opposite realm, it is because humor, like poetry, has an extra content. It plays close to the big hot fire which is Truth, and sometimes the reader feels the heat.
— E. B. White in his essay, Some Remarks on Humour.