I rarely feel jealousy. I get envious if someone else is getting what I need and I'm not.
But-when I'm feeling those negative thoughts-I talk it through with one of my most reliable friends. Reliable in that they never let me get away with my own shit-they hold me accountable to solving my own problems.
I then figure out what it is that I'm ACTUALLY upset about (am I needing something I don't have, am I scared..) and work to solve what is actually upsetting me.
If I feel jealous or insecure about another person-I try to spend time with that person.
I.E. if I'm jealous about my lovers new girlfriend, then I try to spend time with the new girlfriend.
I find that when I build my own relationships with people, I have a much harder time holding onto any type of animosity towards them.
"Love As Thou Wilt"