How does the following quote by Edward Said apply to Brave New World? "Exile is strangely compelling to think about, but terrible to experience. It is the unhealable rift forced between a human being and a native place, between the self and its true home: its essential sadness can never be surmounted."

This quote by Edward Said can be applied, in particular, to two characters: Linda and her son John, the "Savage." Linda, the perfectly conditioned Beta, finds herself trapped on the Savage Reservation. While her memories of her former world are the stuff of comedy and satire, a pathos runs through her inability to adjust to the Reservation and in her deep longing to return home, shallow and inadequate as her consumerist society might appear to us. For home is home:

“... of course there wasn’t anything like an Abortion Centre here. Is it still down in Chelsea, by the way?” she asked. Lenina nodded. “And still floodlighted on Tuesdays and Fridays?” Lenina nodded again. “That lovely pink glass tower!” Poor Linda lifted her face and with closed eyes ecstatically contemplated the bright remembered image. “And the river at night,” she whispered. Great tears oozed slowly out from behind her tight-shut eyelids. “And flying back in the evening from Stoke Poges. And then a hot bath and vibro-vacuum massage.”

Beneath the satire, Linda's pathos lies in her sadness at being severed from her known world, which she has no training to understand and which can only be cured by staying in a haze of mesquite or soma.
Though an outsider on the Savage Reservation, John is even more of an outsider when he travels to his mother's world. He longs for the  Reservation and, perhaps even more, for the world he learned of in Shakespeare: a world in which people feel their pain, suffer, and create art, a world in which he feels people are fully human, not narcotized, conditioned and controlled. He puts it as follows:

“But I don’t want comfort. I want God, I want poetry, I want real danger, I want freedom, I want goodness. I want sin.”

Mond's "brave new world" has eliminated all that and so John feels "an essential sadness that can never be surmounted."