I've ridden three full centuries and countless metric+ centuries in the past few years and I still get anxious in the days leading up to the ride. I think it's totally normal to feel a bit afraid/nervous about how things will turn out, especially when you've never done it before and you've put so much time and effort into preparing so you want things to go well.

I also tend to cry at the finish line.

Sometimes I cry in the middle of the ride, which means that it's time to dig deep into my suitcase of courage. It usually helps to have a snack, too.