John Gottman, the researcher on couples/marriage, found that all couples fight. His wise advice, based on the research, is to accentuate the positive, and minimize, but you won't eliminate, the negative.
What Gottman found is that stable, happy couples have a 5:1 ratio between positive interactions and negative interactions. That is, for every criticism and negative comment there has to be at least 5 compliments and positive comments.
The positive interactions build up what Gottman calls "the reservoir of positive feeling". The reservoir of positive feeling is like a savings account into which you are making regular deposits to be withdrawn on a rainy day. Couples who have reservoirs of positive feelings use some of this when they are criticized to offset their hurt feelings so that things balance out.
How would you rate the ratio of positive and negative interations in your relationship? Do you have at least a 5:1?
I like the idea that Gottman doesn't tell couples they can't complain. He just tells them that there has to be a lot more than that of good stuff if a marriage/relationship is going to be stable and happy. Have you said five nice things to your partner today?