It may seem bizarre to suggest it, but when writing a novel, one of the most crucial things to have is memory, memory of what you yourself have written. There are simple mix-ups, such as when a character says to another character, “Let’s meet at seven, “ and you forget and have the meeting at six. That kind of thing is easy. Most editors—or surely, your copy editor—will pick that up.
(In one of my books, The Man Who Was Poe, the protagonist, Edward, was making a frantic pursuit in a boat. A copy editor kindly pointed out that by my having Edward only tacking the boat to the left, he was going around in circles!)
Much more complex are the subtle elements of character that you introduce, and need to use more than once to establish that character as a living creation. Charles Dickens was a master at this. It’s not enough to use characteristics at a given moment to move the plot forward. They need to be used to establish the character even more. Does the character have a keen sense of smell? A linguistic tic? Left handed? A way of looking at things? Good writing makes use of these things.
As with those characteristics that constitute who you are—over a long life—these elements are vital in what you write over a long book.
Can you remember that?