My T has told me I can leave anytime I wish. I guess I don't see her saying that as a bad thing, she's just making sure I understand I'm not trapped there. Actually, a session early last week, I DID leave early. In 10 months of seeing my T, that was the first time I left early. And I didn't feel bad about it, because she has always made sure I understood that I don't have to stay if things get too hard.
Trying to think of it from a T point of view, I would bet they think many of us feel "trapped" in our lives as it is and they want to make sure we are aware that therapy is a safe place, and we don't need to feel like we're being trapped there, too?
I also retreat, dissociate, so I understand that very well. Once I realized there was actually a word for what I was doing, I was online trying to figure out how to stop myself from doing that. To me, it's embarrassing, and feels like a waste of time if I'm not mentally "there" during a session. Perhaps your T is just trying to help you feel more comfortable....perhaps to say if you start feeling like you're going to retreat, you can always leave before that happens. I know I will be using her offer to leave more often, if I feel like I'm starting to get upset, as I don't want to let myself dissociate, because if it lasts too long, it can cause issues with my leaving. I need to be in a safe place when I leave there. One day, I ended up sitting in a snow bank in a neighboring parking lot, without realizing I'd put myself there. What if I'd gotten in my car and been driving? Perhaps your T is offering this for your safety, and best interest. Just a different way to think about it.