It can be hard to keep them all in focus.
On one hand you want to keep the focus on the bigger issues; if you have to throw out a section as a distraction from the main issue, that you have carefully polished every sentence and word choice only makes it more wrenching and so more difficulty. And if you keep your nose down at the low level, you may discover that you put in foreshadowing or info-dumping three or four times, when you re-read from a higher level by doing it more briskly. Not to mention that focusing that closely can slow you down and be a way of vacuuming the cat.
On the other hand, the biggest picture is rooted in the word choice of the lowest level. Carefully specifying that the beggar woman is hobbling rather than lurching is the sort of thing the big picture is made up of. . . .