Every relationship has its problems and disagreements are a normal part of them. The secret resides in the ability to talk about the hurt in a vulnerable way.
Attachment injuries occur when the injured person cannot trust the other to be there for them anymore. When they talk about the injury, the one who has hurt the other justifies their action and minimizes the other person's feelings. The one who felt hurt might also focus on attacking the other instead of communicating the hurt from a point of vulnerability. Every time they talk about the problem, the victim feels injured again and the hurt grows thus creating more disconnection and resentment.