In order to remake the jellyfish-like hat into something head-sized, I ripped it back to the first two rows which were K2P2 rib. I then kept going with K2P2 rib.
When I'd knitted about an inch and a half, I realized I'd made a mistake three-quarters of an inch back. I'd purled two knit stitches.
I had the old "forget about it, it'll be the Amish mistake, something to keep you humble" conversation with myself, then countered the argument with "what will I regret more, continuing and leaving the mistake or going back and making a hat that when I show it to people I won't have to say, 'Thanks, but there's a mistake right there, see?'"
I went with option B.
Now I am paranoid and check every time I move from one double-pointed needle to another that all the knits are knit and purls are purls.