Jealousy hurts. Jealousy is the belief that there is not enough to go around and that you are the one who is going to miss out. It's seeds are planted in early childhood. It develops and grows in atmospheres of competition and scarcity.
Feel what you are really feeling when you are jealous and you will feel the feeling of competing for something that you consider is scarce.
Sometimes it is the real or imagined scarcity of love or attention that you are competing for.
Sometimes it is felt as the effort to fight others for what is wanted. Sometimes one gives up and sulks. This proves once again to you that there is not enough for you to have.
Actually the basis of all jealousies is love.
In many cases when one is jealous of another this other has things that one wants. That which one wants most is love.
Realize that in reality there is an abundance of things and that you are equally worthy of them and that all that stops you is the belief that you can't have them.
You feel unloved.
In some cases you are jealous of someone's love and see that they are the only person with all the beauty and wonder and goodness etc. and that you desire them.
You may not believe what I am saying at first but everything that you admire in that other is yours already. It is part of you. It has become hidden from you and because you do not see it in yourself you see it in the other. This includes the love which you want.
Do you really love yourself enough to be able to love that other?