I once presented with softwaredoug before a room of 400 people on a project that we didn't quite get finished! Yes... massive amounts of stress as we approached the deadline and realized that we were not going to hit it. Nevertheless, b/c of the stress we pushed harder than we normally would have, we learned a lot more than we otherwise would have, and _despite_ not finishing, the talk was one of the better received of my career. (We turned it into a lessons learned talk. We had plenty of great questions.)
How did we deal with the stress? I think we just sat with it. It was always there. Over time you recognize it for what it is, an illusion. That doesn't make it feel much better, but it gives you a bit more control and equanimity. And being able to push through hard situations despite the illusory feelings of dread opens the doors for doing some really interesting things.
It's somewhat mitigated by the fact that Meetup talks are informal, and in general people like hearing what worked/what didn't work - not perfection. People are generally nice at meetups, especially towards side projects. Of course I'd prefer to show something amazing, but sometimes that doesn't work out :)
(Example if I am interested in a side project, I promise to speak at a local meetup about my work)