The white light is so thirsty that it's like all of the water in his body is being sucked out of his soul realm. He feels like he's going to die if he doesn't wake up. He's got a remnant of the book from his previous life, but he can't figure out what's in it. The reason why he incarnated in the first place was because he had access to the book's contents. Now that he has access to those contents, he'll be able to do whatever he wants with his life.