Working hard is important, but there's something that matters even more. Believing in yourself. Think of it this way: Every great wizard in history has started out as nothing more than we are now. Students. If they can do it, why not us?
Poisonous toadstools don't change their spots.
Harry Potter wasn't a normal boy. As a matter of fact, he was as not normal as it is possible to be.
The more you care, the more you have to lose.
Jiggery pokery! said Harry in a fierce voice. Hocus pocus — squiggly wiggly — MUUUUUUM! howled Dudley, tripping over his feet as he dashed back toward the house.
Maybe he murdered Myrtle; that would've done everyone a favor....