So, before we can explore the toxic topic of "jealousy as a virtue", I guess we need to get a firm grasp of jealousy as a concept.
When used in a non-relationship context, jealousy is often used as a synonym of envy, with envy being that feeling like you'd like to have something that someone else has. It's use as a synonym of envy is obvious in a contemporary sentence like, "Oh man, your new car is totally awesome, I'm so jealous!"
In the context of an interpersonal relationship however, jealousy is far more than a synonym of envy. It's experiencing negative emotions in regards to one person's relationship with another person (other than yourself.) In the case of a person you are in an intimate relationship with, jealousy is often spurred by the feeling that they might choose the other person over you. It's quite common in monogamous relationships, and even some people in polyamorous relationships experience jealousy. The antonym of jealousy in a relationship context is compersion. Not that it isn't possible to experience both simultaneously. Human emotions are complicated.
So, while jealousy can be a very toxic emotion, it's also a very natural one for many people. Learning how to cope with it can be very difficult. This is made more difficult by those who would present jealousy as a virtue, which is what my next post will talk about.
Author's follow-up comment
As of 2025, I haven't actually gotten around to writing the post about how there's a toxic trend that considers jealousy a virtue in relationships. I will one day.