Ester asked why people are sad.
"That’s simple," says the old man. "They are the prisoners of their personal history. Everyone believes that the main aim in life is to follow a plan. They never ask if that plan is theirs or if it was created by another person. They accumulate experiences, memories, things, other people's ideas, and it is more than they can possibly cope with. And that is why they forget their dreams.

Author: Paulo Coelho