Gratitude takes less energy than anger.

But you're better than I am, Katsa. And it doesn't humiliate me. It humbles me. But it doesn't humiliate me.

How acutely sometimes the presence or absence of people mattered

Katsa didn't think a person should thank her for not causing pain. Causing joy was worthy of thanks, and causing pain worthy of disgust. Causing neither was neither, it was nothing, and nothing didn't warrant thanks.

There was no helping her tears. For they would leave Po behind… She cried into his shoulder like a child. Ashamed of herself, for it was only a parting, and Bitterblue had not wept like this even over a death. ‘Don’t be ashamed,' Po whispered. ‘Your sadness is dear to me. Don’t be frightened. I won’t die, Katsa. I won’t die, and we’ll meet again.

Raff, what have you done to yourself? Your hair is positively blue.

Mercy was more frightening than murder, because it was harder.