Your partner says some offhand remark, and now you're on edge. You might shut down or scream. You might cry or self-isolate. You're not even sure why you're so upset, or maybe you are aware of what happened. It's likely that a past trauma was triggered, and this trauma can pre-date your relationship by years and years. That doesn't make it any less real or any less impactful, but it can be something really difficult to manage, and it can strain a relationship.