Congrats on finishing your novel! I don't have any stories to share on completing a novel because, well, I haven't done that yet. Soon. Very soon.  And when I do, I'm certain I'll have feelings of sadness like you described.

Love the Lao Tzu quote. What a great one to spin a story around. It rings true for me in so many ways. I can already tell I'm going to be thinking about that one off and on all day.