Open and honest communication would seem to be the mother of all ingredients in the marriage recipe. If you are unable to communicate freely and honestly with each other (agree to disagree), your marriage will likely diminish. If your spouse tends to dominate most conversations, or if they rarely give credence to anything you have to say, the marriage will not be a happy one.
The old rule was always "agree to disagree" and it followed that each partner could say what they felt and work their way through any issues. So,