Sex for pleasure is just fine. Of course there is a big extra element if love is involved and most certainly Paul and The Goddess are in love, but familiarity obviously lessens this feeling eventually. There is really nothing wrong with just wanting sex. Prevailing culture has a lot to answer for - although don't get me started on morality because that is a topic for political discussion - and most men and woman have a strong biological desire for sex which many have tried hard to deny.
I am at least glad not to be in Victorian times when it was seen as a bad thing and yet 1 in 25 women were prostitutes ... denial is terrible and it seems some people ant to lead us back there.