The other night, I learned a very big lesson in the art of circular knitting, and that is to pay attention to which direction you're knitting in.
I took up the son's knit-from-the-top-down hat and was working away happily on it while I was watching Red Dwarf. After a couple of rows, I noticed a hole in the fabric, as though I did a yarn over, and lengths of running yarn, as though I dropped a stitch. But when I counted, all 104 stitches were present on the needle.
I ripped back (*sob*) and found I figured out that I had started knitting in the opposite direction. I never checked to see the yarn strand was on left and the fabric had the right-side facing. My bad. I was prepared to frog it all and start over (*double sob*) but I thought I'd give saving it one try, and I was successful. The only major hitch was that I lost track of where the fabric joins each round, so I looked for a column of the loosest stitches and used that as my best guess.
I'm proud of myself that I was able to save it, and I'd never have thought it was possible to rescue circular knitting had I not tried. So I guess there were two lessons that were really learned.