Dissociation is a form of protection. We dissociate when our minds need to protect us from some aspect of our reality.
I'm a freezer. My brain has learned that fighting almost always makes the situation worse, and running betrays the panic I feel inside which could also make things worse, so I just freeze up.
I have always been a very sensitive person, and after years of hearing how my emotions were excessive or dramatic or “wrong,” I developed a coping mechanism: always be aware of how others are feeling.