One of the things I do quite a bit of in my practice is work with people who have experienced very serious horrible things in their lives. Sometimes it's random stuff like a car accident. Somtimes is deliberate violence. Somtimes it's neglect. All of these experiences can leave a wound that can't be seen from the outside.
On the inside, there is chaos and hyper vigillence. There can be bewildering intensity of feeling and impulse. Sometimes there is just. . .nothing.
Often, these wounds occurred a long time ago and both the clients and the people around them wonder why they are not "over it". After all, it isn't happening any more.
I always think about this when I watch a movie, in which the main character goes through something totally harrowing and then in the end, is returned to a safe environment. Mostly this occurs in Disney films but I can't just pick on them. In the usual narrative, the horrible thing happens (loss, violence, getting lost, being kidnapped or similar horror), the protagonist overcomes adversity and is eventually victorious, the villain is vanquished and the hero is rewarded. Everything is fine now.
Except, that isn't reality. The reality is that unless our hero is a very well resourced, balanced, well supported miracle of a human (or cute animal in the case of Disney), the event doesn't feel over. The damage can be subtle (constant unease, depressed mood, lack of vitality) or it can be really obvious (flashbacks, night terrors, panic attacks). In real life, these are the people who are diagnosed with PTSD or PTSD-like symptoms and the struggle is real. It's a wound in the mind. A system got turned on and never turned itself off. Time passing can improve it but it doesn't always heal entirely. Sometimes it doesn't heal at all.
Therapy can help the healing process in all sorts of ways. Sharing the present felt experience of a trauma with another person who can hold the story and help make sense of it is healing. Just learning about what is actually happening in the brain when things go off the rails can also help. EMDR (Eye Movement Desensitization and Reprocessing) is another way that a trained therapist can help heal the mind, and make things less chaotic for the traumatized person.
Nothing ever makes it so it didn't happen. But often people can experience a greater peace inside their minds and bodies when they trust enough to do the work. It's work I love.