I'm so sorry you're going through this. I recently had my last session with my T so I know how much it hurts.
Before you go, write down everything you want to say. Try not to bring up anything new unless you think it can be resolved in one session, because you don't want to leave with any open wounds. My guess is your T will try to sew things up so you feel complete when you leave. If there's something you want to say but you're scared, just say it. It's better to be scared than to have regrets about not saying what you wanted to. Finally, just soak up every last minute, enjoy your time with your T. Let your last memories of your T be positive in every way.
Hugs to you, itjustis. <3