Couples are often wondering how to improve their sex-life. Here is a wonderful discussion between Dr. Sue Johnson and Neil Sattin. Dr. Sue Johnson is one of the foremost researchers on love and bonding. Neil Sattin has a podcast and many resources for relationships.
http://www.neilsattin.com/sue2
". . . novelty is like play. An attachment researcher would say that sexual passion is the longing for connection, twinned with attunement (being responsive and engaged with each other) and therefore the ability to play. And where the novelty comes in is in spontaneity and play. The ability to feel safe with someone and talk about your sexual needs openly, being able to talk about any sexual issue or problems openly, about your passion. When you look at it as longing, attunement, and erotic play, that's where the novelty comes in." -Dr. Sue Johnson
