The black and white bull’s-eye appears when I’ve pushed myself too hard. It’s a flickering mark in the center of my sights, like an old film reel blinking over a scene. Physiologically, I don’t know what it is, perhaps related to my blood oxygen levels; but psychologically, it signals when I’ve crossed the threshold from pain to peace. Whereas when I set out on my run or my ride, my brain is sifting, sorting, rehashing, running scenarios, acting out frustrations—all loudly. Once the bull’s-eye appears, all is quiet. All I see is the trail or the road. All I hear is my breathing. Even the thoughts that percolate below conscious contemplation for a time cease to bubble up. And then I know I’ve hit my target; I know I've hit my pace.