Just sent it
Interesting idea that 'letting go' might give the subconscious the freedom to process and release. It would tie in with the most primal / physical forms of release that we talked about above (like shaking etc.): if you're not thinking about it / trying to control it, your subconscious processes it and releases it through your body (which is basically your subconscious).
However, I think the problem is that, unlike animals, humans have that extra aspect of the brain which lends itself to self-reflection. Some people don't "go there" and don't analyse stuff, but they still have that aspect of the brain, and if they refuse to ever self-reflect, in a way they might be repressing it. That also hits the subconscious hard, because anything repressed becomes toxic, and eventually gets reflected back to us in physical reality (our bodies or our lives).
Then there are other people who dwell and ruminate excessively, and that has the opposite effect: creating a kind of inner stagnation because, as you said, it blocks the subconscious from processing.
So, I think what's needed to really process, develop, and mature, is an ability to be conscious of what's happening, but not try to control it. Like watching, taking things in, sometimes reflecting back, but not thinking of a course of action necessarily, because there is no behavioural fix: just the ability of the subconscious to process and release.
Which means that there are things that can be done to "deal with stuff": but they are things like learning compassion for others, building self love, self respect, and awareness. Learning to know yourself, but not ruminating on flaws, or strategies, or trying to change (which is what I spent a lot of time doing).
The problem with the nightmares was that they were so horrific that I never allowed myself to stay asleep for them. I would always force myself to wake up, meaning that I would never fully process them. It was so weird, but I kept having them (always a variation on two themes) until I was doing my yoga teacher training. There was a man on the course who was a "healer", and one night I was having a nightmare, and in the dream he came to me and put his hands on me and healed me. Until that point I was still having 2 or 3 nightmares a week, and after that, they stopped. Maybe I had let go of control sufficiently that my subconscious was able to heal the issue through a person I recognised as a healer.
Now I might have one a month. I had one last night, but before that I hadn't had one in about 3 months.