When my head gets in the way of my writing...
Those times when I am writing a blog post or newsletter, and then my head gets ahead of me and starts editing everything that I am planning to write (and what I have written). Then it starts critiquing what I am writing and I grind to a halt. A that stage I shut the noise off and just let the words come out. That is what editing is for in my book. I can go back and clean up the mess later (if indeed that is what it is), and make it more presentable before hitting send.