But why was the sun also rising?

I am quite puzzled by the title of this book, The Sun Also Rises. The sun plays absolutely no part in the novel. No one really shines or rises or anything like that. I can't think of a metaphor involving the sun, so I am lost. Considering my confusion, I did a bit of research to try to find out the meaning behind the novel's title. I did find out that the original title of the novel was Fiesta. This is actually the title used in the edition in several foreign countries. That title makes sense. They went to a fiesta in Spain for the climax of the novel. So why would Hemingway change the title?
I also found out that the title is a quote from the Bible. The passage talks about generations coming and going and the sun rising and falling and rising again in the same place. I think that Hemingway chooses this passage to show how no matter what happens to a person, they will end up right back where they started. This happens to Jake and Brett in the novel and it happens to every person in their life. Hemingway's novel is about character development, and he shows this through the title.
As the count said on page 67, "that is the secret, you must get to know the values." Hemingway tells us what a good and decent person looks like, but we must figure out how to make that a part of our lives.