Jealousy, Love and Goals

What is jealousy? What really is this emotion made out of? Is it some type of ego infraction? Why is it so destructive...and why ..although you know better, is it so POWERFUL at times. Allow me to give you an illustration. There was a time in my former life (you know pre-1997) when I was seeing someone who was involved with a man, and I had my girlfriend at the time. I would be jealous when she would talk about them going out, getting together, etc. Now that makes NO sense whatsoever. Both of us agreed that we were involved with other people, and we liked it just fine. I was happy in my relationship, but yet, this emotion...would eat away at me sometime.
To this day, there are times when I hear about people travelling, going places, seeing plays, being with their family, just...doing things. I get jealous. And the most interesting thing is...I have ALL these things..and I do all those things. And yet......*jealousy*
Why? It's like insecurities.....my mind can do a dance that is AMAZING....sending me into the pit of scenarios which almost literally drive me crazy. Why? What function does that have? And how powerful is that in my life? I really don't know......but I do know that I want to eliminate it (yeah...good luck huh?)
Well..I'll do the love and goals post another time, I have to finish a petition for relocation here..plus I'm tired LOL :)