Every time they put her on the scale, she crumpled. She was trying to stand, but her hind legs were too weak. Even with two vet techs supporting her, I could see her swollen elbows shake with effort, straining through her thin, patchy fur.

Her toes scrabbled furiously. The four legs splayed out, and she hit the stainless steel plate of the scale again, like a spider that couldn’t balance. I heard the gust of breath whoosh out of her, before the vet techs scooped her up again.

My mother was talking to them about the osteosarcoma. How she’d been 90 pounds, then 60. We’d doubled her Beneful and mixed meat into her food, but her weight kept going down, her ribs coming into sharper relief. Only her big, square head had stayed exactly the same as always: the geometric ears, freckled nose, starry chocolate eyes. In July, when she couldn’t stand another second watching us from the edge of the pool, she’d jumped in—only to start sinking, her 13-year-old doggy-paddle unable to keep her young heart afloat.

Sega, my yellow Lab, turned 14 in December of my senior year. During winter break, my parents decided to put her to sleep.

For the rest of winter break, I couldn’t get used to how quiet the house was. Of course I missed Sega—but I knew she had lived a full, happy life. It wasn’t that I thought my parents had made the wrong decision. I had just suddenly become aware of how quickly I was growing up and how irreversible it was.

My older sister had left for college six years ago. My father’s job required him to work overseas in Asia or across the country in California most of the time, and my mother worked 12-hour night shifts as a nurse. Before, if the silence at home ever became too pressing, it was easy for me to find company. I only had to go as far as the sunroom, where Sega would always give me a welcome kiss. But now every empty room in the house felt twice as large, and achingly hollow.

Subconsciously, it seemed that Sega was one of the last direct connections to an earlier time. Her death, the severance of this tie, pushed me off a cliff. I was afraid of forgetting the past, but I couldn’t stop time from moving forward. Here I was, stuck in a moment when I was supposed to be celebrating my impending induction into adulthood, my foray out of the nest—when all I really wanted to do was spend a little longer in it.

Around New Year’s Day, my mother came home from the vet’s office with Sega’s ashes. She set them on top of the fireplace in a small, locked, mahogany box. School started a week later, and over the next few months I slowly began to grow accustomed to the stillness in the house. I focused on schoolwork until my mother and I had our usual 5 p.m. dinner, with her in purple scrubs. I came to expect the stories my father told when he was home, and remembered to FaceTime my sister.

Whether it happened naturally or was forced as a result of school starting, I stopped dwelling on my fear that I was leaving something behind—and saw that even though my life has changed and will continue to do so, I still have everything I need in the form of memories. I don’t have to live in the past to keep it a part of me.

Today, the locked box still rests on top of the fireplace in my family room. My future is a mystery, but I always know where to find my past.