That day I saw we were not a couple. I was just useful to him. The moment I had a different opinion than him I was (in his mind) attacking him.
I realized the same thing by observing my flatmate and his girlfriend. I looked at them and thought "THIS is a couple!". Of course they sometimes fight as well, but you never hear any of them taking the words "breaking up" into their mouths, no matter how pissed they are.
Unlike my ex who would pack her stuff, leave me, break up with me and start to delete our pictures from our Photostream whenever we had the slightest disagreement.
The moment I realized that you can't really call what we had a "relationship" was the moment I started healing, because I started to realize that I didn't really lose much.