I agree, you and your friend should discuss what will happen if she only wants to go 50 miles ahead of time. Usually there are so many people on organized rides, it won't be like you'd be leaving her on her own.

Another thing that will make it easier for you is just the fact that it's an organized ride- there will be tons of other riders for motivation, and nice (hopefully!!!) SAG stops with good food and cold drinks. Plus, it's always really motivating to go the longest distance ever for the first time.

If you start to feel disheartened and doubtful about finishing your planned distance- eat something! That can be the first sign of an impending bonk- mental tiredness. Calories can really pick you up quickly.

I also almost always get this feeling on really long rides, at about the 65-75% mark of "Why am I doing this, why did I think this would be fun, I hate riding my bike this far" etc. It used to make me feel badly, until I figured out that I ALWAYS felt better once I reached the 80-90% mark, and now as soon as I recognize those feelings coming on, and accept them, and know that they will soon go away- it barely affects me anymore.

Nanci