First of all that's wonderful that you recognize that about you and want to change! I am going go assume you are referring to be jealous regarding your partner. Please talk to your partner. I know it is very stressful when your partner acts jealous and it is not warranted i.e your partner has done nothing themselves to make you feel that way. Could be you have issues with trust that you bring into this relationship. When you notice these feelings coming up tell yourself what you already know: I'm having these feelings for no reason and I'm letting them go. .... You may need some encouragement that you are perfectly imperfect just the way you are ;) Ask for that encouragement from your partner. Give it to yourself.
Ask yourself why you are jealous. Then ask yourself if the reason you are jealous is realistic and reasonable or if you might be overthinking it too much. Ask an honest friend for a different perspective and try to see it from a different point of view. Walk it off till you cool down.