The mind is very powerful and there is a lot to the mind that we don't know and may never understand.
When going through any traumatic event and experience an individual tends to dissociate from the situation in order to escape and cope with the trauma. After repeated trauma, this becomes increasingly easier to do. It's a defense mechanism and even necessary to protect the psyche from further trauma. This not only distorts memories of that time but I think it affects future memory as well, not because of a physical reason or issue but out of learned tendency our minds memory ability is altered.
I'm very detail oriented and because of it I remember a lot of details and can do so for years, but not for all things. Sometimes when I look back on my life, the past feels very surreal and is merely a haze of memories that resemble looking through someone else's mind rather than my own. I have a handful of memories of life prior to my first surgery and that is all, I can only remember about 5 friends from my childhood and barely remember any events. I don't really remember events even with my family, I just know that they were there and I have a strong connection with them from times spent together, I just don't remember what those times were really. As my cognitive development progressed from child to young adult, my memory ability greatly improved but it tapers off again once a few years have passed after an event, especially the chronogical order of events. I don't think this is normal for everyone and I don't think it's a result of age. I noticed these difficulties even during my high school and college years.
Not only does the mind allow for memories to become hazy and distorted as a matter of protection, it also allows for memories to become too realistic reminding us the past did occur. It doesn't take very much for me to recall past pains and physically feel future pain. The feeling of needles, tubes, knives, stitches, staples and all the things that accompany these instruments of healing and torture are quickly remembered and felt even years later. I physically feel the IV in my hands, the central line in my chest, the NG tube in my nose, my abdomen being pulled as muscles are used and the stitches and staples hold my body together against the force. Even now, thinking of the words to type is issuing a call to the past and those demons are clawing at the door to flood my body and mind with those memories and that pain. Before any medical procedure, test or even shot, I have to mentally prepare myself for it and the pain that is to be inflicted - that pain that is all too familiar, at times changing, but never forgotten.
The mind can trick us into false senses of security or can rip us from our safety and plunge us back into tortured memories of the past and the mind brings along our physical body for the ride. That seems to be part of the game though, it's a constant balancing act we must play to maintain sanity during an insane trauma.