In AP Bio, I learned that the cells in our body are replaced every seven years, which means that one day, I’ll have a body full of cells that were never sick. But it also means that parts of me that knew and loved Sadie will disappear. I’ll still remember loving her, but it’ll be a different me who loved her. And maybe this is how we move on. We grow new cells to replace the grieving ones, diluting our pain until it loses potency.The percentage of my skin that touched hers will lessen until one day my lips won’t be the same lips that kissed hers, and all I’ll have are the memories. Memories of cottages in the woods, arranged in a half-moon. Of the tall metal tray return in the dining hall. Of the study tables in the library. The rock where we kissed. The sunken boat in Latham’s lake, Sadie, snapping a photograph, laughing the lunch line, lying next to me at the movie night in her green dress, her voice on the phone, her apple-flavored lips on mine. And it’s so unfair. All of it.