I am a victim of jealousy sometimes. I just figured, I get jealous when I'm not sure about myself. In other words, how insecure I am about my position in the lives of others can make me a monster of jealousy. *laughs*
This is pretty normal in growing up isn't it? We want the people who love us to always keep doing that. If another person slowly creeps into their lives, we might get defensive and exert our so called but non-justified 'ownership' over the people we care about. Indeed, no one has the right to do that. But yet again, not many have the strength to not only think maturely, but feel maturely too. Feelings are immature most of the time. What we are used to feeling in childhood, tends to carry on into adulthood. That's why most of our emotions when invoked, are reminiscent of the way we feel and respond to scenarios since our younger days.
However, the trick is in handling our emotions. If you can't stop but feel them, don't make the excuse that you can't dictate it. We can! I can! Cheers :P