By Gryffindor, the bravest were Prized far beyond the rest; For Ravenclaw, the cleverest Would always be the best; For Hufflepuff, hard workers were Most worthy of admission; And power-hungry Slytherin Loved those of great ambition.

Children's books aren't textbooks. Their primary purpose isn't supposed to be "Pick this up and it will teach you this." It's not how literature should be. You probably do learn something from every book you pick up, but it might be simply how to laugh.

Love is the strongest power there is.

Or perhaps in Slytherin, you'll make your real friends. Those cunning folk use any means to achieve their ends.

Studying the young woman’s long thin legs, Tessa wondered how different her life would have been if she had had legs like that. She could not help but suspect that it would have been almost entirely different.

Never tickle a sleeping dragon.

The realization of what would happen next settled gradually over Harry in the long minutes, like softly falling snow. "I've got to go back, haven't I?" "That is up to you." "I've got a choice?" "Oh yes." Dumbledore smiled at him. "We are in King's Cross, you say? I think that if you decided not to go back, you would be able to…let's say…board a train." "And where would it take me?" "On," said Dumbledore simply.