One of the characteristics of lemon essence is that it likes to improve its sense of superiority by belittling itself. Such people always feel that others are inferior to themselves. Now it is mostly used to express multiple envy of others in a self-deprecating way.
3. Now there is a saying called "sweet and sour lemon essence", which is often used to describe the complex mood of being so sweet by romantic love that you can't help but envy "sour" meaning.