It was bound to happen some time or other; when it did, I was surprised by how simple it was, and how easy to prevent.
I made a noticable mistake on my knitting and kept on going for a good three or four inches.
Sometime yesterday evening (or maybe this morning, but I doubt it), I either added or left out a row. In other words, I worked a pattern repeat of four rows as either three or five rows. This might not be too bad if the front and back weren't noticably different, but as it was I had to pull out a day's work to fix the problem.
Really, it's not so much the mistake that gets me. It's that 1) this happened before I spliced on that third ball of yarn, so I now have a huge tangle instead of a moderate one, and 2) it's a whole day's work. I suppose it could be worse, though: the yarn I'm using isn't one that's hard to unravel - it came out easily, in fact, unlike that mohair that spat a needle and didn't drop a stitch.
Here's to an ounce of prevention.