I think it is true and that as soon as we relaxed a bit I did in fact get pregnant.
However, every time someone said it to me, it took everything in my power not to smack them hard in the face. I totally know what you mean about a magic button to switch off too - people used to say to me, 'stop thinking about where you are in your cycle and just dtd when you fancy it' Yeah that'll help, and exactly how do you stop knowing where you are then?
The thing that DID make us relax was 1. me having some acupuncture and 2. the doctor sending us for day 2 and 21 tests and H's SA, so as soon as we felt someone was doing something.
Which no doubt isn't helpful given your OP, sorry 
But boo and
to you, and you need to develop an Ally McBeal imaginary world where you can in fact slap people when they tell you to relax x