“I’ve been in therapy umpteen years and I’m still struggling with this stuff. The abuse happened so long ago, why aren’t I over it already?”
When someone asks a why question like that, I hear an expression of feelings. In this case, I detect frustration and perhaps anger at oneself. Sometimes an explanation can make inroads by providing a way to transform negative beliefs into compassion for oneself. So here goes.
When you’ve been abused and/or neglected as a child, your development gets derailed. By age three, the brain has already reached 90% of adult size compared to the body’s 15%. There’s a lot of potential there for things to go wrong when you’re so young, helpless and dependent.
The left side of the brain, the seat of reasoning, calculations and language, doesn’t begin to develop until age two, remaining limited till five. The right brain, the site where stress, emotions, intuition, voice tone (the music of speech) get processed, remains dominant till seven at which point language takes over along with narrative, a sense of linear time.
How does the right brain manage stress and what has that got to do with the question?
During times of stress, the autonomic nervous system (ANS) runs the show, outside of conscious control. Initially, the sympathetic nervous system part of the ANS revs up the body to react, either by fighting or fleeing: the heart starts beating quicker, breathing becomes rapid, blood pressure increases, the body readies for action.
Once the threat has subsided, the parasympathetic nervous system part of the ANS kicks in to calm the body by inhibiting the state of arousal, restoring the body’s equilibrium. Too much of this results in dissociation.
When the stressors continue unabated, when the child cannot escape or fight back, the body remains in a state of arousal, pumping out stress hormones, oversensitizing the brain to stress; the ANS ceases to function properly. If the details of this interest you, check out David Baldwin’s Trauma Information Pages  for several articles that address the neuroscience of your problems.
For purposes of answering the question, there’s one more aspect of brain functioning that’s relevant: the limbic system and its role in emotional experience and memory formation. Part of it, the amygdala, a small brain organ shaped like an almond (hence it’s name), processes negative emotions, frightening faces and unseen fear. It communicates with the hippocampus, a nearby part of the brain shaped like a seahorse, where declarative/narrative memory is stored. Integrating information from the senses and other parts of the brain, forming coherent memories of events and placing them in the context of place and time, the hippocampus is essential for learning and memory.
Studies have found a smaller hippocampus in children who have been abused or lived through wartime, in women with severe dissociative disorders and in those suffering from depression. The amygdala is hyperactive in depressed individuals. Memories remain unprocessed, not integrated, returning later as symptoms.
What does all this mean for you? Even though the abuse or neglect happened many years ago, its impact continues because it has taught your brain to react to anything reminiscent of the original threat in the same way it did back then. You might flare into a rage at a slight because you feel humiliated like you did as a child. You might not be able to take an exam because of the panic you experience. Or you might find yourself in a dissociated, spaced-out state, not so much an absence of feelings so much as a disconnection from them. Your stress response system goes into overdrive because of the chronic stress you experienced as a child.
It’s a brain thing and clearly not your fault. It even has a name: Post-Traumatic Stress Disorder.
So look at your progress. Remember when you began your journey of recovery, when you didn’t have a clue about what was ailing you and you were sure you were crazy. Notice how much you have changed. Sure it’s not where you want to be but the work does pay off. The brain is plastic enough to heal. Check out Norman Doidge’s The Brain That Changes Itself  for inspiring stories about neuroplasticity. And hang in there.