In Twilight, many characters fight their natural instincts. It's natural for vampires to drink human blood, but the Cullens work hard to resist this urge. Edward and Bella's love for each other goes against the laws of nature – as Edward points out by stating, "And so the lion fell in love with the lamb…" (13.128) – yet they can't stand the idea of being apart. Other forces of nature show the differences between Bella and Edward's lifestyles. She needs to eat and sleep; he doesn't. He can only lay out in the sun when in trustworthy company; she can whenever she wants. Edward is used to having an immense amount of strength and speed; Bella has trouble traveling at Edward's natural walking pace. The pair may be in seemingly separate worlds, but their love for one another feels completely natural to them.