When it comes to relationships, it is the ways in which we are the same that creates closeness between us.  Shared values, shared world view, shared goals, shared interests, time spent together and so on.   But it is distance and difference which creates and renews desire in a long term relationship.  Because a lot of  couples spend a lot of time together and sleep in the same bed every night, they can end up very deeply bonded on a friendship and love level, yet find that their attraction to each other gets weaker the longer they spend together.  All is not lost though, as there are some very practical things we can do to keep desire alive.