I was working on the YCH commish from last week, and it was looking really good, by my standards anyway. I was really satisfied with the faces and the anatomy was coming together. Then after a combined 8 or so hours of painting it, I hit save on my SAI and my computer instantly shut down. When it rebooted, this was what was in the file. A single layer that looks like this.

Just venting some rage here, the fault is mine, I should have had a backup. It helps also against unwanted weird changes you make due to momentary madness. Feel free to post similar stories here in the comments if you'd like, perhaps if we collectively share our rage it will make us feel better. : P