Jasper is the newest "vegetarian" of the Cullen family, and humans are still hard for him to resist. He struggles the most out of all the Cullens to resist drinking human blood, which is still his "favorite" by far. When Bella cuts her finger at her birthday party, Jasper is the one who lunges, without even thinking. It is his natural reaction at the smell of blood. He has a very violent past as a vampire who drank human blood, and he has a hard time living as the vampire equivalent of a vegetarian.