When I set out on a long group ride I always know there's a good possibility I'll ride part of it, maybe even a lot of it alone because I ride with people faster than me. I plan on enjoying being by myself and I know if I keep my own pace I can finish. I learned this the hard way this past Feb. trying to keep up with my group on a double century. I pushed too hard and had nothing left by mile 160.I was much smarter on the next one I did a month later. I rode my pace and finished by myself and had a very exciting ride trying to navigate alone in the dark&rain. So, my advice is do the ride. Make clear to your group that you prefer to keep your pace and don't want people hanging back waiting(that always makes me tense).Enjoy the scenery and your bike and finish strong.