but I've never been good with change - even when the change was VERY needed.

I'm a very habitual person by nature, very routine, so having my routine thrown off like this is just really messing with me. Of course, as I write this, I'm already feeling much better than I did this morning and I know after my evening workout I'll feel even better!
I am very much a creature of habit now too - I wasn't always, but with the BPD relationship, I began to crave routine - I think it was a way to control what felt so out of control. I am learning to "go with the flow" more and I have noticed that when I am emotionally fragile, routine feels better for me - no right or wrong, just the way it is.
Sharing emotional vulnerability so we are not so alone is very powerful - scary at times, but powerful.
What I can say from my own experience is that once it was all really over, focusing on just me - what I want, what I need, who I am (really) - was much different than when I was married. It was much more real.
Glad you have a T! I hope you give yourself the time alone with him to really dig into the emotions that come up.
Peace,
SB