One thing that seems to happen a lot is that the writer, who is intimate with the topic, and who has been thinking about the topic at great length, forgets that the reader will not have been thinking about the project nearly as much as you. This is true, even if you're a dissertation writer working on a project that is very close to the work being done by professors that you work with. Professors have plenty of responsibilities, so you can bet that they're not thinking about your research as much as you are.
When you forget to orient the reader, then it's easy for the reader to get lost in the details--and, because you're not orienting the reader, there's not a lot of stuff to write except for the details. The material that orients the reader is also the material that creates the framework that makes the details coherent.
If the reader is given too many details without enough material to orient him/herself, then he/she becomes lost in the detail. The reader then cannot see the forest for the trees: all the details are the trees that make up the forest, but the material that helps the reader orient him/herself is the material that says where the trees stand in relation to each other in in relation to the larger forest in which they stand.
There are two main kinds of orientation that you can give the reader: logical and textual. The logical orientation material describes how a piece of the paper--a paragraph, a section--relates to the other ideas that are presented. The textual orientation describes how a piece of the paper relates to other pieces of the paper; it talk about the structure of the presentation of the argument.
Realistically, you want to give your reader a good amount of both kinds of orientation.
If you haven't done a good job of clarifying your ideas, trying to put in this material to orient the reader will be a big challenge. But if you do there's a good chance that you'll have a solid work.