I remember the biggest "foot in mouth" comment of my life when i was a vet nurse, and some children came to see their cat before it was put to sleep. I said something along the lines of, losing a pet helps children understand dying, to which thier mother replied "they don't need an introduction, their father died last year" I wanted the ground to open up and swallow me, luckily for me the mum was very gracious when i grovelled in apology, i learnt to keep my mouth firmly shut as its often best just to say nothing at those sort of times.