I am on my 4th T in three years. The first one was good, and we did a lot of work, but none of my DX's came in until after she retired.
I went through a really tough time when she left, we were together for 18 months and she was my first T. It was hell watching her leave.
The next 2 were different stories, one I dumped after the third session, she had NO clue what she was doing and was a challenge for me to 'educate'

Number three was great, he first suggested DID to me after hearing some tales. I formed a strong bond with him quickly, then 3 months later 'sorry, I'm moving'.
That one was tough as I was fresh into DID, thought my life was over and I was crazy as hell.
BUT, he set me up with my current T who has a background in DID and all sorts of great therapies. We've been together....hell, I don't know...2 years in spring of 2014. I see him at least 2 times a month for 2 hour sessions....and they are harrowing, challenging, troubling, triggering and necessary.
How did I deal with all that upheaval? Well, I have a great partner who is the best 'rock' I've ever found. But, I think with DID, we all have strength that not everyone possesses. We have seen and been through so much that, despite the pain, we carry forward.
I'm not sure what to say, it's hard, it's painful. When you find someone new who really helps it makes the pain more bearable at times.
We could talk about safety and trust until the cows come home here, we all know that trust is the number one trait we look for in anyone else, (whether we accept it or not). I think we need to learn to trust ourselves as much as our partners or T's, in that trust we find the strength to keep tackling these challenges.
I'm hoping things work out for you, there are lots of people here who feel the same and have gone through the same, hope we give you a little peace.