You'll find the quotes by John Green in Quotes & Aphorisms and in Quotes for Every Occasion.
"Some people don't understand the promises they're making when they make them," I said.
"Right, of course. But you keep the promise anyway. That's what love is. Love is keeping the promise anyway."
As he read, I fell in love the way you fall asleep: slowly, and then all at once.
"I'm in love with you," he said quietly.
"Augustus," I said.
"I am," he said. He was staring at me, and I could see the corners of his eyes crinkling. "I'm in love with you, and I'm not in the business of denying myself the simple pleasure of saying true things. I'm in love with you, and I know that love is just a shout into the void, and that oblivion is inevitable, and that we're all doomed...