The most popular causes are financial or economic instability, lack of self control, PLANLESSNESS, and popularly cheating. All of this facts have similar but different effects in which to overcome jealousy and insecurities in a relationship must be treated with different perception.
Financial Insecurities
Financial Insecurities can be overcome by a real plan and consultation. Before you go into this, make sure your partner is sensible enough and accept advice. In terms of saving and investment; many husbands lack the wisdom of saving or investment, all that matters is to squander everything without budget. And this is the most prominent cause of financial insecurities in a relationship which eventually loses itself to jealousy. If this is the case, to overcome jealousy and insecurity in such situation -- plan yourself first. Plan to know how to persuade your man to make decisions before it would be too late. Tell him about the essence of saving or having emergency fund. If this doesn't work, meet a renown and respectful elder or most supposedly councelor to meet him for counsel.
Dealing with Jealousy of Cheating spouse. The only effective way to overcome or even prevent your partner from cheating in a relationship is by taking him all. Do not ignore his callings, be submissive and lively. Say you love him, and always refresh your relationship by daily body maintenance. Stay attractive in order to make his mind fixed on you.
Lack of self control.
Either by abusing you all the time or embarrassing himself and you in the public due to anger; if not married quite the relationship until when you think is proper. If married, pray and commit your spouse' condition unto God. He'll surely answer you! Secondly do not fight because of this, teach him how to be gentle by challenging him in a friendly manner. Just be nice.
What You Should Not Do To Overcome Insecurities and Jealousy
You should not allow past negative experiences to corrupt your behaviour toward getting into new relationship or your action toward your spouse. Do not feel like you are not good enough to control relationship insecurities and jealousy. Maintain a very high esteem within your mind, know how you deserve to be loved and what situation or people deserve to be in your life.
You should be more sincere to tell your wants and what is unacceptable for you in the relationship. This will equally avoid inapproved scenarious which may only happen for real by mistake. With this, try to respect him/her too by knowing controlling your faults.
Learn to observe.
In reality, many relationships fall into jealousy and insecurities due to lack of knowledge of the source of problem. You might be the source. It might be your fault that your spouse is cheating or flirting around. You may have caused the pain and pressure that makes your spouse another man that you've never think of when you first met. Make amendments in sincerity in order to overcome jealousy and future insecurity together.
Be the wise partner.
Do not allow anger or rage to overcome your self. Acting funny might just worsen your situation, therefore you won't easily get how to overcome this insecurity. Stay above anger and don't over react on any situation.