When Do You Know When You've Had Enough?

I said I want to try Dragon Dance and I have been but I never leave practice feeling good about it. I'm very protective of my body parts having injured them so many times so having to run and jump goes against my instict. Plus, the running, oh god, the running...So really, was this the best idea? I'd say no. I'm starting to think I really should be working on my strength and cardio before doing this. It's hard to hear what the sifu's are telling me to do when I'm concentrating on holding down my breakfast. So, what do I do? Bow out now? Shutup and let myself be dragged along? I don't even know. I don't want to slow the rest of the group but the simple fact is that I physically can't keep up right now. I'm thoroughly screwed when we pick up the pace or have an actual dance come up. The demos too, I still haven't changed my mind about those. The forms seminar was bad enough to send me into full blown panic attack and now we have Tiger Challenge...Not sure what I'm going to do about that quite yet. Really, the only thing I'm doing ok with in the I Ho Chaun is the Acts of Kindness, which I'm not logging, so I guess I'm really not doing ok with it... Why am I even here? Why do I keep showing up against my better judgment? There's got to be a reason even if I don't know what that is yet.