This article...

Effects of Conflict and Stress on Relationships

has helped me understand a bit better.

Key point:
"The key is to learn and continually hone your conflict resolution skills. Being able to recognize and identify your feelings and express them clearly, learning how to be an active listener, and practicing assertive communication are just a few skills that can help you handle relationship conflict in a healthy way."

I still feel that my pain is disproportionate to the level of conflict, but this article suggests that the longevity of the unresolved conflict is the issue. In my case this is sibling conflict, and I can imagine how it will resolve, which helps, but still is very painful and tiring