Create a buffer between yourself and the necessity of the task. It's cliche, but I love to take a walk. I find that my mind reliably wanders away from the thing I'm trying to do. And when I remember it, as I walk, I can feel excitement rather than pressure, for coming upon the problem as if by chance. It's a little cheat, a self-inflicted head trick. Every time this happens, it makes me realize that you're never ready to do something well until you want to.