One other suggestion I have to help you stay up with the faster group is to warm up before the ride. At least for me, that makes a huge difference in eing able to keep up on group rides. My ideal warm up is--for whatever reason--9 miles. Even if I can just get 4 or 5 miles in, however, I do much better and my legs thank me for it.
Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.
--Mary Anne Radmacher