First, they are exalted- they are astonished that it can be so simple to create the general "working plan" of an article. They seem to find it especially hope inducing (strange word choice, no?) to see a blank page or a cacophony of rambling words quickly find a potential form.
Next, they write. They usually pick the easiest section in which to write, and then just go for it!
Then, the depression hits-"look at this rambling mess that I have! I will never be able to make sense of this, even with this structure."
Lesson- once you begin to write a section, you need a structure, or an a architecture to that section. This does not mean that you have to create a million sub headings, or that you must create this structure before you start to write (in fact, you should not do this, as this will usually lead to a lot of useless obsessing and "contemplation.")
Yet, once you have been working on a section, you need to think about how it fits together. What are the "take aways" you wish to give the reader? How should the section and its various components support the overall aims of the article?
One tool for helping you do this is to print out a couple of copies of the section, and literally cut and paste the various sentences and paragraphs. Rearrange them on a table, and see what fits and what does not. What is missing?
Regardless, try to work on the structure of your sections without compromising your writing! Go to another section, and make sure you get some writing done as well. In this sense, you are engaging in writing, THEN editing, not writing and editing. Always remember that writing and editing are two different functions. See post Write THEN edit