I’ve experienced extreme jealousy when a former boyfriend’s (female) friend was blatantly coming onto him (while she was enjoying my hospitality for an extended time) and he did nothing to discourage her. I got so worked up about it that I demanded he cut her out of his social circle, which he did. I’d handle the situation differently now. In fact, had I given it some serious, rational thought back then, I would’ve worked out that the situation arose out of some deep-seated issues with my relationship with my boyfriend. As it was, I addressed the symptom and not the disease, which led to the eventual dissolution of the relationship.
I hardly ever experience jealousy now. I’m older, more secure and don’t have nearly as many trust issues. Also, I don’t feel like anyone is actively sabotaging my current relationship.