If I had a plot that was all set in advance, why would I want go through the agony of writing the novel? A novel is a kind of exploration and discovery, for me at any rate.
I think the hardest part of writing is revising. And by that I mean the following: A novelist has to create the piece of marble and then chip away to find the figure in it.
I think that to a very great extent we are partners with the divine in this enterprise called history. That is an ongoing relationship, and there is absolutely no guarantee that things will automatically work out to our best advantage.