Psychological physical injury

I have a question for those who have had a psychological, physical injury.
Those who know what I mean realize I'm not talking about the injury not being real and it being all in your head, but a physical injury so traumatic to the body and brain that the brain remembers it and constantly leaves you feeling pain as if the injury happened just yesterday.
Or put another way, the brain refuses to forget and is in a constant state of 'fight flight' and everything triggers these injury memories.
Have you been through this?
Can you share your story of how you overcame it?
Thanks IM's