Blue Valentine shows in the plainest possible way what happens to so many of us all the time: The breakdown of relationships. Cianfrance doesn't offer many answers to all the questions that are piling up in the course of the film. The two story lines are very loosely woven, and just hint at the underlying mechanisms of this particular relationship.(...)
The script can often be contrived as hell. For example: The old boyfriend and the male doctor are poorly written and their black/white nature doesn't fit with the rest. Why did she sleep with him on the first night despite the fact that she was pissed at her boyfriend that he ejaculated and risked making her pregnant? These flaws make the story feel like an excuse for the performances which are it's saving grace.
A look at the very sweet beginning and the very brutal end of a relationship. The two moments intercut back and forth, so when you see their puppy love develop into something that may work, it cuts back to the end to prove you wrong. It’s not a happy experience, but it’s damn good.