Luck can only get you so far.

But some part of him realized, even as he fought to break free from Lupin, that Sirius had never kept him waiting before. . . . Sirius had risked everything, always, to see Harry, to help him. . . . If Sirius was not reappearing out of that archway when Harry was yelling for him as though his life depended on it, the only possible explanation was that he could not come back. . . . That he really was . . .

Don't be stupid, it's a flying house!

It was so good to be held. If only their relationship could be distilled into simple, wordless gestures of comfort. Why had humans ever learned to talk?

To the well-organized mind, death is but the next great adventure.

Ah, go boil yer heads, both of yeh", said Hagrid. “Harry — yer a wizard.

Oh, it can't be a reference to the fact Harry's a great Seeker, that's way too obvious. There must be a secret message from Dumbledore hidden in the icing!