Wouldn't it be strange, she thought, to have a blue sky? But she liked the way it looked. It would be beautiful - a blue sky.

A darkness different from Ember's, but just as frightening.

There is so much darkness in Ember, Lina. It's not just outside, it's inside us, too. Everyone has some darkness inside. It's like a hungry creature. It wants and wants and wants with a terrible power. And the more you give it, the bigger and hungrier it gets.

Doon was touched. Kenny looked like a tiny little wisp, but there was something strong inside him. --People of Sparks--

They lifted their faces to the astonishing warmth. The sky arched over them, a pale, clear blue. Lina felt as though a lid that had been on her all her life had been lifted off. Light and air rushed though her, making a song, like the songs of Ember, only it was a song of joy. She looked at Doon and saw that he was smiling and crying at the same time, and she realized that she was, too.

The main thing to do is pay attention. Pay close attention to everything, notice what no one else notices. Then you'll know what no one else knows, and that's always useful.

A person who thought he knew everything simply didn’t understand how much there was to know.