When Draco was young, he learned that spells like the Patronus charm were Light, Gryffindor spells, charms that a true Slytherin would never be caught uttering.
When Draco Malfoy is older and he has met the Git-Who-Won't-Die, he reminds himself of what he learned and looks on in disgust as Potter struggles to learn these spells of Light. Later, when he is laying in a heap on the Quidditch field's grass, grinding his teeth, he pretends that what causes his jealousy and hate is the fact that Dumbledore and all the Defense Against the Dark Arts professors favor Harry Potter over everyone, not the fact that Potter can do something Draco can't.
A night later, in a dark abandoned class room, there is a boy who whispers the same incantation over and over again. Overtime, the boy learns that memories of first broomsticks or of Weasley's misfortunes are not enough. Satisfaction and glee are not part of the right types of happiness.
In spite and frustration, the boy drudges up a memory of when he was little and sick and miserable and of when… Mother sat by his bed and told him stories and Father missed that really important meeting with the Minister just for him.
A silvery light glows at the end of his wand before going out. The boy stares for a long, long time.
Three weeks later, a silver ferret crawls up the boy's arm and nuzzles its snout behind his ear.
When the light finally disappears, Draco reminds himself that a true Slytherin would never be caught uttering that spell. As he closes the door to the dark classroom, the Malfoy heir is still smiling, A warmth lingers in the room and in the heart.