So I was sitting on the sofa, quietly crocheting, when the ball of yarn got stuck under the sofa. I thought I could just pull hard at the yarn to get it out. But no, I could not. It was thoroughly wedged under the edge. The force of my yanking (er, that sounds almost rude?) resulted in the (soft, peaceful) cotton yarn cutting into my finger. Ouch.
Learn from my lesson: do not yank your yarn, lest ye cut yourself!