I don't dissociate but i think my daughter does. (I have also posted elsewhere that I think my husband does when he's under extreme stress too). She was in an orphanage until she was 14 months old. After we adopted her, when we put her in the crib at night she would throw crying, screaming fits for up to 2 hours, and nothing we did helped. She would "zone out" and you could pass your hand in front of her face during those tantrums, and it was like nobody was home. If you crossed her about anything (told her no) she would go into a rage and seemed to dissociate. But that was when she was a toddler so I'm not 100% sure.
But when she was 11 she had a traumatic brain injury when her horse fell with her. She was in and out of consciousness for about 12 hours, and then afterwards had total amnesia. (She was so sweet and compliant; I never thought I would be glad to hear her be sassy again, but I was!) ... Her memory came back in bits and pieces until finally months later it was mostly back. Still, years later, if she meets an old school teacher or somebody she hasn't seen since the injury, she might not remember them.
Her psychologist said that the amnesia can't be explained by the injury itself because it didn't do that much damage to the brain. She cracked her skull in two places and had a bad concussion, but no deep tissue damage to the brain. His opinion was that the amnesia was dissociative. So that kind of confirms that she had/has a tendency to dissociation.
What I know about dissociation is that if you have very early trauma, it changes the brain in such a way that you "compartmentalize" certain memories. And we know that memories and other cognitive processes are highly influenced by emotion --- so everybody finds it easier to remember things when you are in a similar mood or emotional state to when you learned the information. People who dissociate just take that to the extreme. You might not remember whole chunks of your life experience except for when you enter an emotional state similar to the one you were in when the memory was made. And while for most of us we can eventually access the information by thinking hard and trying to make associations, when somebody dissociates its much harder to just retrieve the information at will.
The way the brain works just fascinates me ... how there are all kinds of mechanisms (like dissociation) that help us survive. I know, though, that eventually stuff like this makes your life very very difficult.
Let me know if I can help in any way ... about the only thing I can think of is looking up information for you if needed.