I think narcissists' obsession with control stems from the fact that they feel they are worthy of everything. If they want something, they deserve it and if they don't receive it, it's like the world has come to an end. And so they try to control situations and people to make sure that they are always getting what they want-- whether it's love, attention or praise.
It's very difficult for people to live with narcissist because of their controlling and selfish attitude. People cannot constantly give love and affection without receiving any in return. But when a narcissist gives affection, even that is pre-calculated and serves a purpose for them.