our brains cannot distinguish between fictional and real people, so when you fall in love or become friends with a fictional character, your brain doesn't know that they're not real. And then the book ends, the character dies, or the journey is over, and you suddenly don't have those characters anymore. your brain's first instinct is to mourn, and that's why it's we feel so sad when something happens to our favorite characters. knowing this doesn't change anything, you just know it now :(​