When I try to read a textbook cover to cover, I find myself much more concerned with finishing rather than understanding. I want the satisfaction of being able to say I read the whole thing, every page. This means that I will sometimes cut corners in my understanding just to make it through a difficult part. This ends in disaster once the next chapter requires a solid understanding of the last.

When I read a textbook, I try to solve all exercises at the end of each chapter (at least those not marked "super hard") before moving to the next. That stops me from cutting corners.