surely a load of nonsense. If the goods have already reached their destination a bit of fun can't surely do any harm. No one suggests against enjoyment whilst diffed. Can't really take this advice seriously to be honest. Like you say, it's stressful enough anyway, and I think keeping your relationship healthy is important too. Especially as you don't know if the 2ww will come to anything. I think it would impinge on your swi the next month personally as it would make it even more about timing rather than relationship.
Thank you - that's what I think too! I suppose the concern might be that if implantation is in the process of happening it might be thrown off by contraction type movements...at least that's the only thing I can think of that even vaguely makes sense! I have decided to ignore it anyway. (And most of the rest of her book to be honest.)