Harry Potter and the Order of the Phoenix (Harry Potter, #5)

by J.K. Rowling

“Then you will find yourself easy prey for the Dark Lord!” said Snape savagely. “Fools who wear their hearts proudly on their sleeves, who cannot control their emotions, who wallow in sad memories and allow themselves to be provoked this easily — weak people, in other words — they stand no chance against his powers! He will penetrate your mind with absurd ease, Potter!”

And I’ll see Sirius again. . .

Youth cannot know how age thinks and feels. But old men are guilty if they forget what it was to be young . . . and I seem to have forgotten lately