One can see an analogy between writing a dissertation and making a large scale visual art project.
To prepare for making a painting or other large work, artists have drawn studies of their works.
When they draw these studies, they are comprehensive--they shows the whole of the work in a rough form. They allow the artist to explore different relationships of elements, to explore how the work will appear when complete.
If the writer of a dissertation tries to perfect a part of the dissertation, a chapter, for example, without working on the other parts he or she cannot be aware of how the piece relates to the whole. It's like a portrait painter trying to paint the eyes perfectly without painting any of the rest of the face.
Like any analogy, this one is of limited use. But it is not uncommon for writers to get stuck because the chapter they are working on isn't "done."
The point of the process is not to write one chapter, but to finish an entire thesis. Understanding the overall structure--seeking to find or construct that overall structure--greatly facilitates the writing of an academic work.
Draw a study sketch of your work--sure it's rough, sure each piece is poorly defined, but it creates a vision of the overall work that you can't get any other way.