Act as a seasoned poet with a deep understanding of structured verse and emotional depth. Craft a sestina that explores the theme of loss, using the six repeating end-words: [TEARS], [MEMORY], [EMPTY], [SHADOW], [WHISPER], [FADING]. The poem should evoke a sense of [GRIEF/LOVE/LONGING] while adhering to the sestina's strict form. Incorporate vivid imagery, such as [A WITHERED ROSE], [A FADING SUNSET], or [AN UNANSWERED LETTER], to deepen the emotional impact. Ensure the final three-line envoi weaves the end-words together in a poignant resolution. The tone should be [MELANCHOLIC/REFLECTIVE/BITTERSWEET], and the language should feel [LYRICAL/RAW/ELEGANT].