I've noticed something about my husband since we got married. When things go wrong, no matter if it's a small thing like an electricity bill that is higher than we anticipated, or if it's a large thing like potentially losing our homeowners insurance after neglecting a piece of mail, he is very interested in assigning blame.
I'm not sure if this is his way to prevent the problem from happening again, or if he's just being a jerk, but sometimes when I am talking to him in moments of stress, I notice that the words "your fault", or "my fault" come up more often than I find necessary. Obviously I don't like being blamed for things by my husband. This irks me.
I've noticed something about myself too. I am very, very, very defensive. Sometimes I sense a "tone" coming from my husband that, upon further prying, I realize is non-existent. Sometimes I scoff and make a sarcastic, defensive comment only to get a quizical look from him, saying "I wasn't accusing you of anything." I'm not proud to say it, but sometimes I literally create tension and conflict where there isn't any.
Nagging, blaming, and defensiveness are all huge stressors in a relationship. Not only does nagging not help you get what you want, but it makes the person on the receiving end feel like they are not good enough and that they need to change in order for the relationship to get back on track. This leads to stress, resentment, and defensiveness.
Defensiveness is a relationship killer because it makes communication difficult for all parties involved: they can't hear what are trying to say, and you can't hear what they are trying to say. Next thing you know, you're both defending yourselves against attacks that aren't real. Stop wasting energy on damage control, and focus on working together to solve the actual issue.
The dynamics of blame, nagging, and being defensive with your partner are ones I am quite familiar with, though I am nowhere near conquering them.
What I do know is that developing a healthy team mentality with your partner is a lifelong practice that takes patience, conscious thought and effort, and vulnerability. And the first step is taking your share of the responsibility for making it happen.