Bluebeam. I think the tendency to catastrophise when you are feeling distressed and abandoned is pretty common - I know it is for me. "Everyone has gone, forever, terrible things will happen and I won't be able to cope alone..." etc.
I also think that times of absence of a trusted supporter can feel worse because of the whole safety net concept - the knowledge that you normally know you have that safety net if you need it, which somehow gives you an added sense of security and confidence which mean that you probably won't need it afterall. But the knowledge that that safety net is in fact not there can increase the anxiety and prompt you to feel you need it, even when you otherwise wouldn't. Sorry, not sure if that made sense.
Try to focus on the little things you are achieving and coping with in T's absence, and look forward to being able to share those with her when she returns, along with a discussion of the things you found most difficult or challenging. I know it sounds silly, but it might even help to almost think of this time as like a homework exercise - a chance for you to test out where you're at and report back later with the successes and the areas to work on, to help you map the way forward when she returns.
Sorry if that sound silly or unhelpful, but sometimes I've found that it can help a little with the sense of isolation to think that you can use the difficult time constructively, and knowing that you will be able to talk it all over soon...
And hey, another day is behind you now!
Maddog