I know what you mean. I first was exposed to this community by Neil Strauss's "The Game" and he mentions this same thing. If you think about it everything we learn when we're young a lot of the stuff we get in trouble for ends up helping us later. We're all taught that it's bad to interrupt or talk to strangers and thus, as adults we have a subconcious desire to not approach strangers who are amid conversation.

I struggle with this kind of stuff myself but have never had a situation turn out bad that I actually open. Thus, I'm of the opinion that there's no such thing as a bad ice-breaker becasue if you engage someone else everything else is simple by comparison.

That's really nice, I see that you are making progress. that feeling you got on your first approach will always be there, the trick is to get used to it, just like sky divers.