The quote reflects the unexpected and powerful nature of love. It conveys that love can arrive suddenly and without warning, reminiscent of a thief sneaking in during darkness. This metaphor highlights the surprise and intensity that often accompany deep feelings. The speaker acknowledges that they cannot explain where this love originated, emphasizing its spontaneity and mystery.

Additionally, the expression of love causing one's heart to "burst" suggests that it is overwhelmingly positive yet intense. This imagery embodies the depth of emotion tied to loving someone deeply. The author, Philip Pullman, captures the essence of love as an unpredictable but transformative experience that can profoundly affect one's emotional state.