I believe the real meaning of the movie, from beginning to end, is that every relationship is unique! Every relationship, whether it be that of a same-sex couple, a single, sex-crazed female, a childless couple who consider "days off" from the marriage, or working mothers who find it extremely difficult, has its own rules. Each couple, or individual, must make up the rules that best fits their lives and circumstances. Also, families are unique and individual as well.
In our society, fortunately, we see the uniqueness of relationships and families everyday. The blurring of the past traditions is somewhat confusing and hard for some to grasp. Tradition is important, but we cannot stop the hands of time. No matter how much one dislikes it, society is in constant change and evolution. Nothing can remain the same. We have to realize this and move on with society as it changes.