I'll join the chorus in what has already been said. I felt the same apprehension before my first (and so far only) century 2.5 months ago, also with TNT. Our last training ride was 72 miles and I barely survived the last 6. It took every ounce of my being to refuse to SAG. You can imagine the shot that my confidence took- I immediately figured if 72 gave me a hard time, how would I finish 100?

But doing the actual century is an entirely different animal. You'll be amazed at how much your mental state can effect your abilities on that day. I remember how energized I was just by the sight of so many other people attempting to do the same thing as I was. If you have done the training, you can do it. Its merely a mind game at this point. There were moments on that day (most specifically the climb on mile 85!) that were pretty rough for me, but I never doubted whether I would finish. It was an absolute.

I know that will be the case for you. Don't be so worried about finishing that you don't take the time to enjoy what you are doing! Taking those moments will provide additional energy to you. Good luck!