All I can say is that I know the cycle we can get in when sex and intimacy in general is lost between a couple. In many cases, there is no fault as in there was no choice in the matter. Rekindling intimacy is extremely difficult due to the differences between the sexes. My wife used to say that I needed to romance her into a sexual mindframe, yet she has issues with me get to "close". In other words, she needed love to have sex. Where as me as a man, I essentially needed sex into order to have love. It was hard for either of us to initiate, especially since I had issues that even if we did get to the point of having sex, I may or may not have had an orgasm. Not a lot of motivation.

Ultimately we spent time working on intimacy in general, without the context of sex being involved. Once we were comfortable being "close" to each other again, we were able to move back to sex, though it's never been like it was in the past.