every post so far has been dead on (botto would be in heaven). next week you'll be in just a tiny bit better shape from working as hard as you did. next week take an easier day the day before, stay in the draft, conserve as much energy as you can, and you'll do better if not stay with them.
training is basically overload then recovery. if you ride with a group you can hang with, thats not an overload so 1 you won't be motivated as much to keep up as the faster group and 2 you won't get as much of a gain from it