Well, I learned some things today.
For the first time ever, I brought the work I've been making to a craft fair, and offered it to the general public. On the whole, I did a good job. I had some good lists from doing my research and thinking about how the process might go. I had a tasty and filling lunch that I could put down if I was interrupted by customers. I had a water bottle. I was lucky that friends came so I could take a short bathroom break (Hi Kate! Hi Abby!). I was lucky with my table, and I had a couch to sit on.
For a day that was an utter bust financially, I learned a lot of useful things, most of them "don't panic." Had more people come in, I probably would have sold more, it was just really, really quiet today.
But - I have a data point. And I can do it again, knowing more this time.