You know, I think its a process. I am reading a book at the moment "Trauma and the struggle to open up" and the main theme seems to be that learning to trust after complex trauma is a process that takes a long time and is marked by a pattern of making progress quickly followed by protection, over and over again.
Using cognitive strategies like you are doing here helps. It makes it faster and easier to regain your footing when the protective strategies are triggered. Some people make progress in one session then want to jump ship altgother (quit) before the next session. It's hard to be vulnerable. It can be terrifying to be vulnerable. Maybe its okay to honor that process within yourself... as a child it truly wasn't okay to be vulnerable, so now you will have to actively learn how to do that. It will eventually come to pass, after dipping your toes and then retreating to self protect, many many many times over. If you can find a way to see and hold the overall process then maybe you won't feel so swept away in the flow of the tide in the moment.

I do think your logical brain will be able to influence your emotional brain of this... but perhaps your emotional brain will need to actually experience the ebb and flow of trust and retreat before it truly understands.

I have been with my current T for one year now and I am only just beginning to think or feel about trust with her. Up until now I have steafastly denied any vulnerability but now I find us going through the tidal flows of reaching out in trust followed by retreat. I hold the overview of it, it helps. I tell myself this is just part of the process. Like you I think my t is actually quite trustworthy. That doesn't automatically undo a lifetime of trauma and enable trust to be, unfortunately.

One day, eh?