" You see, Ross, in every right marriage, in every good marriage a woman has to be three things, don't she? She's got to be a wife and look after a man's comforts in the way a man should be looked after. Then she's got to bear his children and get all swelled up like a summer pumpkin and then often-times feed them after and smell of babies and have them crawling all about her . . . But then, third, she has also to try and be his mistress at the same time; someone he is still interested in; someone he wants, not just the person who happens to be there and convenient; someone a bit mysterious . . . someone whose knee or -- or shoulder he wouldn't instantly recognize if he saw it beside him in bed. It's -- it's impossible. "

― Winston Graham , The Black Moon (Poldark, #5)