A long time ago, before writing novels, I remember finding myself, late at night, trying to put a book down, then getting angry because the ending of the chapter forced me into the next chapter.

Dark circles under my eyes were a typical pattern for me. And that was why.

Ending your chapters with tension, questions, or emotional impact leads to more curiosity and therefore a need to continue forward.

Readers should feel compelled to turn the page...therefore, the addition of dark circles.