You're dealing essentially with a paradox, like setting out for the other shore by means of which one learns that there is no other shore. The presence of a long-term, conscious goal has helped me to maintain stability through the ubiquitous changes of over half a century. But books have last chapters. It is the responsibility of the writer to devise that last chapter with such care that the reader's thoughts can flow back over the story as if it were a varied terrain under flood water. The trivial is inundated and the high ground visible.
Lives have last chapters too.
The very process of approaching that last segment of work gives me pause. But we flow our minds back anyway, whether we want to or not. The picayune disappears and the significant rises to glow in the light. Each of us will see a different mountain. Our individual perceptions dictate the relative magnitude of factors in that backward view.