Albus Severus," Harry said quietly, so that nobody but Ginny could hear, and she was tactful enough to pretend to be waving to Rose, who was now on the train, "you were named for two headmasters of Hogwarts. One of them was a Slytherin and he was probably the bravest man I ever knew.

It does not do to dwell on dreams and forget to live.

Hearing voices no one else can hear isn't a good sign, even in the wizarding world.

It was a shame, but as Ron said, you couldn't have everything in life..

Really, Hagrid, if you are holding out for universal popularity, I'm afraid you will be in this cabin for a very long time,' said Dumbledore, now peering sternly over his half-moon spectacles. 'Not a week has passed, since I became Headmaster of this school, when I haven't had at least one owl complaining about the way I run it. But what should I do? Barricade myself in my study and refuse to talk to anybody?

You might never fail on the scale I did, but some failure in life is inevitable. It is impossible to live without failing at something, unless you live so cautiously that you might as well not have lived at all - in which case, you fail by default.