When I first began writing seriously (meaning, I took myself seriously and took writing courses and joined writing groups and forums in order to improve my craft), one of the things I learned was that much of the discovery of what your book was about -- the theme-- was rarely apparent in the first draft. Or even in the second. It wasn't until you'd been through a few extensive rewrites that you began to see the theme.
I noticed this when I wrote "A BUTLER'S LIFE," about Chris's experiences as a formally-trained English butler. (Oh boy, don't get him started on the reality of domestic service vs. Downton Abbey!) A Butler's Life is a memoir, not fiction, so I wasn't consciously seeking a theme. But an unexpected epiphany occurred as we read through the drafts I was editing. A pattern emerged. While Chris had never consciously realized it as it was never a caregiver situation, every one of his major career choices was made in response to his relationship with, or responsibility towards his father...right up to and including his father's death. (And later, outside of the timeframe of the book, the impact of my father's death on him precipitated another major life change, which eventually led to our buying a bed and breakfast inn.) The pattern, an unexpected revelation of motivation, unintentionally shaped the story told in A BUTLER'S LIFE.
It made me think about how rarely we stop to consider the timeline of our lives...usually not until we face a terminal illness or old age do we take the time to look back and try to find the patterns in and meaning of our lives. Journal work is good for this, but how often do we actually read back through our journals and do the work?
Do you re-read your journals, to look for consistencies in thoughts and behaviors, or patterns over time?