Jealousy is not at all low, but it catches us humbled and bowed down, at first sight. – Sidonie Gabrielle Colette

Jealousy lives upon doubts. It becomes madness or ceases entirely as soon as we pass from doubt to certainty. – Francois de La Rochefoucauld

Every other sin hath some pleasure annexed to it, or will admit of an excuse: envy alone wants both. – Robert Burton, The Anatomy of Melancholy