Khaled Hosseini said this quote

Mammy was soon asleep, leaving Laila with dueling emotions: reassured that Mammy meant to live on, stung that she was not the reason. She would never leave her mark on Mammy's heart the way her brothers had, because Mammy's heart was like a pallid beach where Laila's footprints would forever wash away beneath the waves of sorrow that swelled and crashed, swelled and crashed.