What are the most impactful/insightful quotes of the series for you?

I don't mean the funny or dramatic moments. I specifically means quotes from specific statements that you think about a lot or sum up a specific feeling or concept to you. My apologies if I'm not phrasing it correctly. My example would be from Distant Cousin:
"It’s weird to think about people who knew you as a child. You change so much, and when you talk to them again, they’re not talking to you. They’re talking to someone else, someone you used to be. The person they think they’re seeing has been dead for years, but they didn’t see the change. They’re looking at a complete stranger, and they have no idea."