Don't be afraid. Think about how proud of yourself you'll be when you cross the finish line. I did my first (s) this summer. The MS150 is designed to be 75 miles each day with optional century loops. I planned to ride 100 each day and did. The second day was hard with tons of hills and even some pea gravel stretches, but I finished. The first day was so much fun, with all the adrenelin and pack riding. Just go out there and have fun and then pat yourself on the back when you're all done! Good luck! Is your ride supported in any way? We had rest stops every 15-20 miles with food (fruit and bagels mostly) and water or gatorade. I am sure that helped.