I finished reading this list of 100 books - voted for by the British public - last year. The book that came third in this 2003 poll was actually three books in one - His Dark Materials by Philip Pullman. This trilogy is usually categorised as children's fiction, but I read them all as an adult and gave them 10/10 for enjoyment. Pullman is a brilliant writer.
This quotation is from the first of the three books - Northern Lights (known in the USA, the cinema, and perhaps elsewhere as The Golden Compass). Short and simple.
"You cannot change what you are, only what you do."