i think only new pain can make you get over old suffering. positive ones cannot cover negative ones. why is it black and white

Living through new painful moments, I realize how much the old ones have lost their weight. Yet why is it that negative experiences seem to have the power to overshadow past suffering, while positive ones rarely overshadow earlier joys? Does it work in a black-and-white way, where only pain can silence pain, just as happiness might try to soothe happiness? Even in moments of joy, I still remember the old bright ones, though they grow hazy and distant with time. Why does past suffering lose its hold, even when, in that moment, it felt as if my world was collapsing? Why can’t positive experiences dim the shadows of negative ones? It seems that only new suffering gives me the strange clarity to understand—and finally let go of—the pain that came before