Jealousy does not necessarily pose a threat to relationships. Sometimes it can be helpful in spicing things up.
The easiest way to understand this would be to think of it this way- suppose your partner said to you that they don't mind who you sleep with. They would probably come across apathetic. Jealousy in moderate amounts has proven to be good for relationships. Too much and you have a disaster on your hands.
"Jealousy is always about three people" said Dr Leahy, as quoted by The Independent. The third party could be someone that your partner is interested in or someone that is interested in your partner. Either way, you feel threatened.
Insecurity may have less to do with the third party and more to do with the kind of experiences you have had in your past relationships, say, a partner who may have cheated on you or walked out on you. Or it could be because of the high expectations that your partner couldn't meet. Another factor could be commitment issues on your partner's end.
Dr Leahy further said, "Sometimes jealousy can be a consequence of high self-esteem that makes another person's behavioural flaws more apparent in comparison to their own e.g. someone saying 'you can't treat me that way!'"
Jealousy can be divided into two categories- sexual jealousy and jealousy regarding emotional closeness. Studies show that men are more affected by the former and women by the latter. The idea of their man falling in love with another woman is devastating to women.
There are certain ways to overcome any kind of insecurity. Recognize that being jealous is normal. Give up the interrogation, the controlling, checking their social media and phones, and the following part. If you are still dwelling on it, spare yourself some time and pen it down.
Sit down with your partner and talk about the dos and the don'ts. If all else fails, know that your life is not restricted to your relationship with your partner and accept that sometimes it's just not meant to be. Part ways with them if it doesn't work out....