It seemed weird calling a teenager 'sir' but I'd learned to be careful with immortals. They tended to get offended easily. Then, they blew stuff up.

He looked at the silver pocketknife in his hand. An idea came to him – possibly the stupidest, craziest idea he’d had since he thought, Hey, I’ll get Percy to swim in the River Styx! He’ll love me for that!

Nico wasn't sure whether to kick himself or Will Solace. If he hadn’t been so distracted bickering with the son of Apollo, he would never have allowed the enemy to get so close.

Don't talk to my sister that way.' Nico said. His voice quivered, but I was impressed that he had the guts to say anything at all. — Percy.

Nothing lasts forever. But the thing is, you can reuse some. Use your mind. - Leo's Mother, The Lost Hero.

Fear can’t be reasoned with. Neither can hate. They’re like love. They’re almost identical emotions. That’s why Ares and Aphrodite like each other. Their twin sons – Fear and Panic – were spawned from both war and love.