Lostalgia
It might have been the 96% humidity in the air, or it might have been the fact that no matter what economists say, some things don't change. The buildings might have been newly constructed, but the hands that built them are old. The dogs that nuzzle under the ancient rusty bicycles might be young, but their lineage is ancient. If mutts have lineages, that is. The kids who run to the school bus are just more recent models of him and his friends from twenty years ago. Minus the He-Man bag, plus the cellphones.
Going to the place you grew up is supposed to fill you with nostalgia, not nausea. It's supposed to bring back only the good memories, not the half-wished ones, not the curbed dreams, not the unfulfilled desires, not the unfinished stories.
As he walked these streets again after twelve years, he finally found resolution in one distilling thought - he had left to fill others' cup with good memories, to fulfill dreams and desires, to finish the story - for others. And that is what matters in the end.
That someone's walk down memory lane is nostalgic and pleasant because of him.