I had my mouth pressed into the sand. I was breathing hard—desperate, shallow, uneven. I could feel the grains entering my nose, throat, and lungs. Somewhere nearby, I heard the rapid thudding of hooves, the panicked exhale of a frightened horse. For a moment, I couldn’t remember where I was. I couldn’t piece it together. The memories didn’t come in order; they arrived like broken glass, sharp and disjointed. My helmet. My shoulder. The ground. Pain. Sharp pain. A blinding throb in my...