Reading your post reminded me of my chemo. I was anxious to start and also so sad. I can remember crying in the shower that morning. Then I pulled it together and slapped on my big smile and off I went. It's okay to feel frightened, sad or nothing...as long as you turn up.
I felt very tired after chemo due to drugs so wasn't fit to drive. A number of hours later I just felt weird and thought I would be sick (I wasn't but felt it) it was scary for me. It was only a couple of hours for me alone but I recall feeling I needed someone there just in case. So if you can have someone there for your first day would be good. Or at least someone you can call if you don't. The 1st one is very unknown, many people have no issues. I wasn't one of them and eventually required additional days if steroids plus 2 antinausea meds. I was on ACT-H. ...you certainly wouldn't be gaving the H.
I had someone with me every chemo (not herceptin) so I had someone to chat to. My unit was small and no division between chairs and same nurses so we often chatted and I got to know other patients so we chatted too. I often dozed but struggled with reading because of meds. Everyone is different. Colouring books can be good to pass the time.
Best of luck and let us know how it goes. Kath x