He was born into a poor nobleman. He loved reading novels and wanted to become a wandering knight to eliminate evil.  He brought the armor of his ancestors to arm himself, named his thin horse the steed Rocinante, and himself the knight of Mancha.  He secretly loved a peasant woman so he gave her the name Princess Dulcinea.  He was skinny, lanky, riding on the back of a scrawny horse.  In the end, he suffered from the delusion that he was a wandering knight