"You're expecting to much of yourself.[•••] For a thirteen - year - old wizard,even an indistinct Patronus is a huge achievement." - Prisoner of Azkaban- Professor Lupin talking to Harry.
I like this quote because it is inspiring. Harry pushed himself a little bit and through determination and perseverance, he achieved what he wanted to achieve. He could have given up trying to cast a patronus but despite the unpleasant effects the Boggart had on him, he still kept trying. It's also a reminder that any difficult patches we might go through to achieve our goals can make us stronger and sometimes we can exceed other people's expectations of us.