If you let a woman sleep around, then she will, because she thinks, that if you let her sleep around, then you don't really love her. What a woman really wants is for you to be territorial, and tell her in no uncertain terms that she is your personal property, and no one else gets to touch her. She'll even forgive you for your personal polygamous tendencies, when she knows you aren't going to get rid of her, for some other woman, permanently.