Martin and Barresi:

Religious contextualizing aside, it is clear that a new ideal of romantic love had emerged. What made it new was that it portrayed love as an affair of the heart at the core of which is service to the beloved. In Europe, before this time, love, especially between husband and wife, tended to be thought of as a practical arrangement. While there may have been no precedent for the new ideal, either in pagan or Christian sources, there is a source: twelfth-century troubadours, especially William of Poitiers, who expressed in his love poems that the lover’s happiness is dependent on that of the beloved and that service to the beloved is an important component of a meaningful life.