I've had an emergency c-section and a planned c-section more recently.
I know exactly how you feel, I did feel exactly the same way. I know everyone will say 'oh you'll be fine' and expect those words to help, but I know that nothing I say will calm your nerves. Just keep thinking about all the exciting things to look forward to with your LO, what they'll look like, cuddling them and being able to hold them very soon. The time will drag and I recommend getting as much sleep as poss in the days leading up to it.
This time round on the day I was surprisingly calm. I had been so organised that I was bored waiting around to go into hospital! You just go with the flow on the day, take a magazine to read until you go down and some nice snacks. Try thinking of lots of positive things.
The planned section this time was exciting, but I was nervous walking down to theatre. I had a spinal put in and I must admit it took longer than my epidural and it was quite painful, a nervewracking experience and I found it very hard to stay in the position when they were trying to put it in. I started to panic, and as soon as it was in I felt sick, but just remember the staff are always lovely and will reassure you. I'll reassure u now too that as soon as everything was in place, I was given anti-sickness meds which worked brilliantly and from that moment on everything will be fine. In my case they didn't tell me they'd started, it was a weird experience, there was music on in the background and I was chatting to the staff and my OH.
Just go with the flow, realise there is nothing you can do to change it or make it happen in any other way and if there is any point that you feel nervous, panicky, uncomfortable or weepy, just remember that 'this time too will pass' and let things just tick by, take deep breaths and you'll get through.
Relish the time before meeting your baby when the time goes slow, coz after they're born the time flies by! x