Sometimes I fall in love with the underpainting, wishing I was done. Wishing that I didn't have to move farther and thus possibly screw up something I liked. But you've got to quickly get over that to move forward.
When I got around to painting over the underpainting, I chose to use payne's grey, which I hadn't gotten my hands on before. Little did I know that when I mixed it down with white, it looked really blue. So when I finished painting the final, I was like crap, its super blue! I kind of liked it but knew that I wasn't done.