The culprit is common, everyday resentment.
Resentment is a perception of unfairness for not getting the expected help, recognition, appreciation, consideration, praise, reward, or affection. It is becoming a predominant emotional state in the age of entitlement. But it builds under the radar - by the time you're aware that you're resentful, it has reached an advanced stage.
The problem with resentment in families is that much of it is due to the effects of emotional pollution tracked into the home from the outside. Resentment is a way to blame powerless feelings on someone else, and the rule of blame is that it usually goes to the closest person. Blame justifies self-righteousness and low-grade anger, which temporarily feel more powerful. But the temporary empowerment comes at the cost of making an enemy of the beloved.
The Chain of Resentment
No one resents just one thing. The continuous nature of resentment creates a self-linking chain, whereon past resentments attract present offenses, forming an ever longer and heavier chain. For example, I had a client who came to his first session resenting his wife for going to bed without kissing him goodnight. That event linked onto the night before, when she tried to kiss him while he was pouting over the fact that she wouldn't help him do the dishes. That linked to the night before, when she did the dishes behind him back, implying that he wasn't capable of doing his household chores. You get the idea, once bound with a chain of resentment you can resent someone for doing something and for not doing it.
A point about the architecture of a chain is worth noting. If you pick up a chain by one link, you hold not just that link but the weight of the whole chain. The chain of resentment does not distinguish important matters from petty or trivial ones - they're all links on the chain and therefore carry the weight of the whole chain. That's why nothing is too petty to resent.
Though mainly about the past, the chain of resentment eventually extends into the future. That's when your expectation of someone disappointing you becomes self-fulfilling prophecy: "The weekend's going okay so far, but she'll find some way to screw it up."
How it starts
Resentment exists in all enduring relationships, because even the best of them cannot be fair all the time. It builds automatically as interest declines, an interest must in all relationships that pass from novel and uncertain to familiar and stable.
The trouble comes when resentment blocks natural compassion for loved ones. In good relationships, compassion - caring about the discomfort or distress of loved ones with a motivation to help - outweighs resentment. When resentment begins to overwhelm compassion, it forms a self-linking chain that makes you look for things to resent, as protection from disappointment. At that point it starts a downward spiral of irritability, impatience, restlessness, bickering, cold shoulders, stonewalling, angry outbursts, and, eventually, emotional abuse.
Here are the signs that resentment is building to danger levels. Either you or your partner is:
• Judgmental about the other's perspective without curiosity to learn more about it
• Irritated by how the other feels
• Intolerant of differences - you should see things the same way
• Irritated by things you used to think were cute - facial expressions, laughter, tone of voice, manner of dress, etc.
• Making less important things more important than the most important things, e.g., the towel in the middle of the floor is more important than your emotional health and the well being of your relationship
The cure is to understand that resentment covers a deeper hurt, even when the things you resent seem petty. Increase your:
• Core value - get back in touch with the most important things to and about you, which will not include resentment and anger at people you love
• Compassion for yourself - recognize that when you are resentful or angry you are hurt or overwhelmed; focus on healing and improving rather than punishment
• Compassion for your partner - recognize that when he or she is resentful or angry, he or she is hurt or overwhelmed; try to help
• Respectful negotiation - you have equal value and equal rights
• Recognize the effects of emotional pollution.
Couples inevitably develop automatic defense systems (ADS) once they start blaming their negative feelings on each other. The ADS is mostly triggered by non-verbal cues of body language and tone of voice, but is primed by the effects of emotional pollution. The best way to disarm it is to view it as something happening to both of you rather than something one is doing to the other. You should be able to say, "He our ADS got triggered, let's regulate it so we can feel connected again." Together you can disarm the ADS and other effects of emotional pollution. Blaming your partner merely contributes to more emotional pollution and makes you both more defensive.