For as long as Draco can remember, his father has imposed it upon him that he must hate this Boy Who Lived. This boy who is a mockery to them and everything they fight for. And Draco is young and impressionable, so the hatred comes easily. He feels the words roll around his head with surprising ease, and the tight burning in his gut feels as if it's always been there. He doesn't know who Harry Potter is or what he looks like or what he likes or anything about him at all, but Draco knows that he hates him, and none of that matters.
Everything changes the day Draco meets him -- the day he stops being the Boy Who Lived, and starts being the boy who lives, who's sitting in a train compartment with unbrushed hair and broken glasses, looking unimpressed by his surroundings. The familiar burn of hate within Draco becomes alien, and yet it's exactly the same as it always has been. He clenches his jaw when he speaks, and he can feel a tang of copper in his mouth; when he turns away from Harry, he doesn't feel angry or spiteful. Rather, it's something akin to disappointment and rejection.
No one warned him about what would happen if he didn't keep his hatred in check, and fell onto the wrong side of the spectrum.