The trick is probably to do it in a really exaggerated way, so it's obvious, after the first big guffaw, that not even you yourself can really think you're that

The trick is probably to do it in a really exaggerated way, so it's obvious, after the first big guffaw, that not even you yourself can really think you're that much of a klutz / idiot / weirdo / whatever aspect of yourself you were making fun of.