I dreaded the last session too. It's hard but it was so beautiful as well. People don't always get to say goodbye to their loved ones. This is a chance to have a proper goodbye.
Take this opportunity to say and ask everything you want - but I agree with Annielovesbacon to leave out things that can't be resolved then and there. You'll need the closure.
In the sessions before the last one, T and I talked about our last session. We agreed on writing down everything we wanted to say and read it to each other. It was intense, emotional, validating, reassuring and I felt so very loved.
Maybe ask for a hug if you've always wanted it but never dared to ask. I took the chance because I'd regret if I didn't. He was very happy to hug me and I felt so loved again.
Try to relax and enjoy every minute of being with your T.