I agree with Stig on not being put off group rides. It's all about finding a group you're comfortable with. And it's another experience that, with the right approach, adds to the riding experience and your skill levels. Leaving plenty of room between you and the other riders, "riding your own ride", not fixating on the bike or lines of the rider in front, staggered road positioning, making sure the guy in front has a chance of seeing you in his mirrors and allowing him room to not worry about where you are, having organised arrangements like the drop-off system and routes planned in advance, all well briefed before setting out - all these things help to make it safer and less pressurising for all. And you do still have a certain amount of responsibility to others in the group, if only because what you do can affect those others.
And yes, there's still a risk that things can go wrong. But that is just part of life - you can stay sitting at home, all snug and safe and warm, and (assuming the house doesn't burn down!) you may live a long life. But that's not living life is it?! The trick is to learn from the mistakes of both yourselves and others, and take whatever precautions you can.
I'm constantly analysing my riding and I know I often still contradict myself in both word and deed. But I guess that's only human, biking is, after all, an affair of the heart and, like many on 2 wheels, I'll get carried away in the moment sometimes. And one thing I think I have learned, is when to back off, slow down and rethink my approach to any given ride out. And if it doesn't feel right, I won't do it.