Insecurity is a recipe for ongoing unhappiness. Insecurity can come from your own self-judgment, or from the judgments of others. Either way, it makes no sense to go through life under the yoke of that judgment.
If you are being the best version of yourself possible, living the life that is true and right for you, no one has a right to cast judgment on you. That includes your own doubts.
Remember, you picked them up somewhere along the line, and they are unfair to you and to others. The people who love you now love you for who you really are. You do neither yourself nor them any favors by constantly second-guessing their affection and respect.
Jealousy usually stems from insecurity. If you can let go of insecurity, you can often let go of jealousy, because you no longer spend all your time worrying about what you are going to lose.
Possessiveness is an emotion closely related to jealousy. Sometimes it causes it, and other times it results from it. It’s one emotion which will bring nothing but harm to those you love, and also to yourself.
Remind yourself when you are feeling possessive that a relationship is not something you own, but something you share with another person. You will feel much happier when you leave that ugly emotion behind you.
You may even discover once you let go of possessiveness, jealousy, and insecurity, that you never had anything to worry about.