My T retired and we terminated because of it but she gave me over a year's warning and I'd been seeing her for 7-8 years already.

Retirement/termination/death/being left is very upsetting but part of life and I would work with your T hard now and in the next 6 months to explore this whole "problem"/pain and see if I can come to peace with it better. I think leaving now without any closure would make things harder in the future, no matter what the future holds.