Insecurity can wreck relationships because of how much power it has over a person. Someone lacking in self-confidence will find it tough to look past their doubts and see the bigger picture. This can create massive problems in relationships, especially if the reason for insecurity is unfounded.
A man on Reddit shared how his wife confronted him after he had a conversation with a woman wearing a bikini. Interestingly enough, his wife shared her side of the story, and her version was quite different.
More info: Reddit Original/Update