My wife and I were together through very thick and very thin for a few years before we tied the knot and I think the reason it's really working so well is that we were both painfully aware of our shortcomings and honest about them. I know damn well that I'm an obnoxious ass for about half of each day so I've never expected her to like me all of the time; I don't like me much sometimes, either. So we try not to get pissy with the other person when they say "Hey, you're being a faggot, piss off k?". What am I going to say if my wife calls me a faggot? I'm on KF; I'm a faggot.
When things aren't going so well we usually just do the chilly civility thing for a while until we're ready to communicate properly and make up. There's bickering here and there and the occasional bout of loud voices and flashing eyes, with the attendant stompings off for a walk and a cigarette but most days it's nice, if not great.
I guess what I'm trying to say is that the secret to my marriage so far is humility from both sides; we're human, we can be kind of shitty sometimes, everybody feels bad about it, tries to do a little better next time, and life moves on.
All in all, I'm happy with where we are now.