I also go there feeling that I just don't want to share, but that's how I've trained myself to be. It's actually helping me being here, as Perna says, and trying things out in a non-threatening environment. I don't think you need to feel shame about the state of your life, I don't think anyone here would agree with you about that, just feel sympathy for you and want to support you. If the people in your group are ordinary, decent people they would be the same. Part of the process in the group is facing up to your fears and going outside your comfort zone (in your own time). Whatever you manage to talk about with them (whether staying or having a break) will be a great step forward. Good luck!