When I feel jealousy, I ask myself why, but with more detail. As in, "what am I afraid of losing if he loves someone else?" or "why do I think it takes away from my value to him if he enjoys another woman's company?" or "what does being upset buy me?" I try to take a step back and examine my jealousy as if I were a scientist looking at a specimen. So, I usually discover, and have to come to terms with, some insecurity or fear I have.
And then I think about the person I love, and remind myself that when I love someone I want them to be happy and feel free and unencumbered by any neediness of mine. I remind myself that I want him to express who he is fully and not keep him small just because I am feeling insecure. I don't want to load him down with my insecurities, baggage, and tears. I remind myself that I want him to be with me because he wants to be, not because he's obligated to be, and if I give him the space to be himself and enjoy life, he will come back to me. I then say to myself, "Why wouldn't I want him to have as much love go his way, as he can possibly get?"
This process of questioning, and then reminding myself of the best ways I know to love him, usually puts me in a good state of compersion. And then, sometimes, it just helps to put on some upbeat music and dance in my underwear, or go do the dishes.
The world opens up... when you do.
Oh, oh, can't you see? Love is the drug for me. ~Bryan Ferry
"Love is that condition in which another person's happiness is essential to your own." ~Robert Heinlein