If one thing is vital to a writer's day, it is the morning pages. It helps absolutely. Whether you call it Morning Pages, or Novel Diary, it jump starts a writer's day. In the morning when you haven't primed yourself up yet, and you are groggy from sleep, you need this.
I've been practicing writing the Morning Pages, and it has worked wonders. I get more easily and quickly attuned to a writer's mindset. I get focused in what I need to do during the day. I can make a link with the previous day's work, and then continue from there.
Just as a journal can be useful to any person, these pages are useful to a writer. I am a living proof. They are even more needed after a weekend, when I don't write, to go back to the working mode. I forget my work during the weekend, which I devote to my family. So, getting back to work on Monday is a bit tough.
I have to orient myself to the stream of thought. I have to pick up from where I'd left. The novel's complexity comes back when I delve deep into myself, and that I can do when I write my pages.