You might wonder how in the world telling your intimate memories of traumatic events could make such a difference. Here's how I see it.
I think there comes a time for every "victim" when they come to believe that they will never, ever be able to tell what happened to them. They've lived with the secrets for so long and feel so isolated that they give up. The decision to remain silent is then reinforced if their supposed rescuer betrays them, if they tell and are not believed, if the abuser is vindicated or ignored, or if someone implies that they should have or could have rescued themselves.
Oh, they might reveal the bare facts of the trauma. Over the years, I told lots of people something like, "Yeah, I was sexually abused as a child. A minister molested me for several years and then my father continued it at home." Short and sweet. In each case, I was absolutely certain that nobody would care, nobody would understand, and that it would only make people uncomfortable and lower their opinion of me.
Real healing comes from finding a safe listener (ideally a professional) who is committed to hearing your whole story without judgement. That includes how you felt, what you saw and heard, what you thought about - all of your fears, worries, horrors, humors, anecdotes, and lies. It's amazing what a relief it was to finally share that part of my life with a doctor who encouraged me, sympathized with me, and challenged my self recriminations.