In the quoted passage from "Lolita" by Vladimir Nabokov, the speaker reflects on the clarity of understanding a past destiny compared to the unpredictability of a destiny that is still unfolding. This contrast highlights the ease with which one can interpret previous events when all the pieces of the puzzle are in place. The speaker suggests that looking back allows for a more straightforward narrative, revealing how past choices led to current situations.

However, the idea of a destiny still in development is likened to a complex mystery that cannot be easily unraveled. Unlike a well-structured mystery story where clues guide the reader toward understanding, real-life situations involve uncertainties and complexities that cannot be easily deciphered. This underscores the challenges of living in the moment and the difficulty of knowing how one's choices will shape the future.