Blue Valentine is a hard movie to watch. It shows how the institution of marriage can be a trap to be wary of. It works for some, but for others, it might be destructive.
It also underline how manipulative some people can be and what tools they can use. Love does not conquer all, the same way as unconditional love is a sickness, not a value to be held high. Some people you cannot help, and you have to save yourself and those you love.
Not for the emotionally sensitive.