All 4 Uses

nostalgia
in
The Fault in Our Stars
(Edited)

It didn't have any of the cloyingly bright primary color-painted walls or the framed paintings of dogs driving cars that one found at Children's, but the absolute sterility of the place made me nostalgic for the happy-kid bullshit at Children's.
p. 231.8

nostalgic = longing for something in the past
Gus said, "I wish we had that swing set sometimes."
My nostalgia is so extreme that I am capable of missing a swing my butt never actually touched.
p. 236.1 *

nostalgia = longing
"Nostalgia is a side effect of cancer," I told him.
p. 236.2

nostalgia = longing for something past
"Nah, nostalgia is a side effect of dying," he answered.
p. 236.2

Definitions:

(1) (nostalgia)
happiness that come with the memory of good times combined with a hint of sadness that those times are over
(2) (meaning too rare to warrant focus)