Welcome to the site.
I had the same feelings as you described.
Also, one of the things I remember is the feeling that, because I was told that successful RT was my only chance that the cancer could be cured, I just hoped that everything had gone ok. I walked out of the last session feeling the same way as I used to feel after taking exams at school, my future depended on whether I'd done everything right. I know the only thing I could do is to make sure my bowel was empty and I had a full bladder but I realised that those four weeks (I had 19 sessions) were the most important weeks of my life. It was a scary thought.
You can feel isolated after the regular visits for RT, but for me it helped to join my local Prostate Cancer Support Group around about the same time. Perhaps you might consider this if you're not already a member.
Anyway, may I wish you the very best of luck with your treatment and keep in touch and let us know how things are going. You will find some good friends here.
All the Best,