I had an interesting experience over the past 13 years. I had a female Cocker Spaniel growing up from 3rd grade up all the way through college. Before her, dad would come home all pissed off going on a tear - and then Angel showed up. And even when she was just a little puppy, she would jump on his pillow with legs spread - when he would come home on a rant he'd look at her - her legs noticably shaking with "i'm gonna blow...just say another word." And magically, the yelling went to "angel...please get off my pillow." and of course she did it.
She died a week before I got diabetes in 2003 - but when I lived at home, even after she died - her cage was always in front of the door so it was impossible to get inside without setting her off.
And when i'd come home late at night, i'd find myself tiptoing not to wake her up, completely oblivious to the fact she was no longer there.
Case and point - i think the idea of training animals is a misnomer. They train us.