Insecurity in relationships is an issue that I have gained a great deal of knowledge on. I have gained most of this through first hand experience and obcservation of family and close friends. I see two main sources of insecurity in relationships. Lack of trust, and a bad self image or feeling of helplessness.
Lack of trust really causes many more problems than just insecurity, but there wouldnt be one without the other. The most common thing I notice happening when there is little or no trust in a relationship is constant anxiety. Never being completely sure of a relationships status, or knowing whether how to feel about the situation. It easily causes arguements, which will make things even more unstable.
Another thing that causes lack of trust is the past. A cheating boyfriend, a friend hiding things, or family members excluding you for a period of time can really effect on the amount of trust that will be given later on if the relationship is continued. Its very hard to completely forgive and forget, and for that reason it can really make a relationship feel completely insecure for both sides.
A bad self image is something that creates insecurities in many different relationships. But more often than not it makes a bigger impact on intimate relationships. When a person feels like they arent good enough for their partner, or they dont feel good about themselves, it rubs off on the bond that those two people have. Whether that persons partner aknowledges the insecurity, or not. Most often it is used against that person and turns into a controlling relationship.
I beleive that when things get to the point in an insecure relationship wbere they become controlling, its the feeling of helplessness that takes over. Both partners feel for one reason or another that they cannot leave each other. One may feel like they cannot be without the other. Or they might feel like keeping things the way they are is the easier road to take. Both are very unhealthy. The insecurities continue, trust issues keep arising, and once resolved issues become reoccuring problems. But they continue to feel helpless in their situation and are afraid to change their circumstances.
I dont know if insecure relationships are worth continuing on, or if they can be fixed. I think the best thing for them however is time apart. Especially when self-image is an issue. You cant feel better about yourself when you are trying to hold yourself to someone elses standards. Trust is something that is easily lost and hard to regain. Sometimes impossible to regain. But hopefully the value of the relationship outweighs the insecurities holding it back.