I can totally relate. I am right there with you. It hurts. It hurts so much you just want them back and would do almost anything to make that happen.
I am so sorry that you are going through this, as others have said just try to be as kind to yourself as you are able in each moment. Sometimes that will be more than others.

My situation is a little different as I am still holding out the faintest hope that my T will change her mind and return to practice, but I am also aware that this is possibly the denial stage of the grieving process. I am glad that you are seeing an interim T.

The only thing that has made things a little easier for me is trying to make my T proud of me. I do believe that she wants the best for me, so I am trying to live up to that. I am trying to eat healthily, exercise, rest, enjoy life and am seeking another therapist. All the things I know she would want me to be doing. That is what is keeping me going right now.

Is there any way you could maybe write to your old T every few months maybe? To keep some form of contact?

When I left my first ever T, she left the door open. She said I could always reach out if I needed to. She couldn't do therapy with me, and she made no reference to what reaching out would look like, but that branch SERIOUSLY helped. I emailed her several times in the first couple of years, when things weren't going well with the new T, or when I needed a rational ear, but in the end it was me that decided not to see her again, and not to email again. I decided that it wouldn't be helpful any more. 5 years on when my other T just upped sticks and walked out I did contact her, and she was there for me. She is now helping me (apparently!!) to find a new therapist to work with.

When I emailed her initially to say that I didn't want to meet up, she said that she thought it wise, and that it was a decision that she had been hoping I would come to by myself.

I think that is a long way of saying that some people truly understand abandonment and the incredible harm that it can do. Some people don't seem to get it as much. When it is 'us' making the decision, it can be done in a healthy way. It gives us some control back, maybe. When that decision is made by someone else it just opens up all of those old wounds again.

I don't know if that is helpful or not!! I am truly sorry that you are going through this, and as you can see from all of these posts you aren't alone. Here you have a community of people who will understand far more than most of the other people in our lives. Take some comfort in that and hopefully you will find your way through it all. Hugs if you would like them.

Oh, EDIT, and journaling. Something I have never really done before but felt an overwhelming need to do. I got a notebook and I just wrote. Whatever was in my head. To her, about her, about anything and everything. I can't talk to her about these things any more but the notebook gives me a place to get some of these thoughts and feelings away from me a little.