An hour ago, when leaving work I was absolutely freaking out about tomorrow, and for the first time ever I called T and asked her to help me calm down. At first she was a bit shocked when I explained the situation, like she made me tell her 3 times what kind of appointment I have tomorrow. I think she wanted to make sure she understood this right, as she absolutely didn't expect it. She wanted to know why now, what had made me do it and so on. At that point I was like: please T, let's not analyze this now, I'm freaking out here!!!
She understood this, and we talked about different coping skills I could use to calm down a bit and help me through the night.
She also put things into perspective saying tomorrow is only a first interview, I won't move out tomorrow, and I can still back down if I'm too scared or can't do it. But that simple fact that I called and asked for this appointment is a huge step forward. I also haven't been this distressed in a really long time and she asked me not to consider it a relapse, that I'm doing something so huge for me, that being scared is to be expected and that I am making progress even if I don't feel like it right now.
She gave me some advice for the appointment tomorrow and asked me to keep her up to date on this, had to remind her that we actually have a session tomorrow. (I don't have regular sessions because of my work schedule) She was really happy about this and said we'll discuss it more tomorrow.

By the way, I made another huge step forward today: My supervisor asked me to work tomorrow and at first I told him that I had appointments to go to and probably wouldn't be fit to work. He wanted to know more and I decided to be honest and asked him if we could step out. Once outside I gave him basic information, and he was absolutely supportive. Immediately told me I'll have the day off tomorrow, to do what I need to do, and in the future to let him know whenever I need some time off.
As it was only 3pm, I offered to stay 2 hours longer and make the delivery that was plannd for tomorrow today to help the team. When I got back from the delivery he took me aside and said he really didn't expected what I told him. But he will support me any way he can, to call him if I ever need to talk and no one at work will know. And he's crossing his fingers for me tomorrow! Had I known he would react like this I would have told him sooner. This is a huge weight lifted off my shoulders!