I totally agree. Write and let yourself fail. Many writers will talk about "vomiting up" material before going through a process of revision. You have to get words down on paper, and frequently, that process will be blocked by being too critical of the words you are typing. Don't be too critical. This may go against our tendencies as programmers to write worthy code from the start, especially from the TDD perspective. When you are writing creatively, you don't have to generate fully functional (i.e., beautiful) prose right away through micro-iterations. (Write a line, look at it, does it work, refine the line, does it work, look at the paragraph, etc -- that's not the way many pro writers work.) Spew it out, then refine.

After I wrote the above paragraph, I recalled the recording of pg working on an essay (http://etherpad.com/ep/pad/slider/13sentences) and how different it would probably look if it were Stephen stream-of-consciousness King. There's a lot of backtracking as pg hones his words, sentence by sentence. It would be really interesting to see how authors of different backgrounds approach the creative writing process, and whether target work length (essay vs novel) and style (argument vs entertainment) dictates your approach.