The Lightning Thief
How we cite our quotes:
They protested, and it was hard to let them go after all we'd been through, but I knew I had to do this last part of the quest by myself. (21.9)
Being isolated for so much of his young life helps Percy be a bit independent and helps him recognize when he has to do something on his own, like delivering Zeus's master bolt. It takes great courage to march up to Mount Olympus all alone as a twelve-year-old boy.