The phrase "live and breathe something" means to have a great passion or devotion for something. There are various synonyms for this expression, including "eat, sleep, and breathe something," "be obsessed with something," "be a devotee of something," "be crazy about something," "be fanatical about something," "be enthusiastic about something," "be passionate about something," "be devoted to something," and "be addicted to something." These synonyms convey the same intensity of love for something that makes it an integral part of one's life. Whether it is a hobby, a job, a person, or a cause, "living and breathing" it shows an unwavering commitment to that particular thing.