What makes a marriage last?

Being a Marriage and Family Therapist, I have studied marriage and relationships for a long time trying to understand why some last and others do not.    I have studied experts like the Gottmans and Sue Johnson(EFT) and gone through training like Prepare-Enrich. I have looked at marriages I know and studied the marriages of people in the media. There are so many theories and formulas that people use and then there are societal norms that people ascribe to without any basis in fact or theory and both are used for people to predict if relationships are going to "make it" or not.  After lots of learning, studying, and lots of work with couples over the years, I think I have an understanding of what makes a relationship work. I really think it all comes down to Character and Commitment.  If you are a person of character and commitment and you find someone with character and commitment, the relationship is destined for success.  I have seen people make it through the pain of an affair and couples that become closer through chronic illness and cancer, but on the other side I see couples just decide to be done with each other or move on to a new relationship with less to no apparent stressors to bring it about.  WHY?  It is all about who the people are and what they signed up for.  If a relationship has the two Cs they can make it through anything.  Success isn't found in living together before marriage(sorry, that one has never made sense to me), how long you date before you get married, having the same beliefs in the main categories, or the same or opposite personalities.   Success isn't found in finding a person that speaks your love language, because while that book(The Five Love Languages) is great, when you love your partner in a sacrificial way and you have the 2 Cs, that person will feel loved, even if the two partners express love differently.  It isn't about the age that you met and get married, I have seen couples meet in high school and make it through life together and I have seen couples meet when they are older and it doesn't make it.  
So, let's talk about the 2 Cs.  When you have character; you are honest, respectful, kind, transparent, and have the qualities that enable you to put another person first and not do actions that are intentionally selfish and hurtful.  This is not to say that the 2 Cs keep people from hurting each other, we are definitely all human, but there is a difference between an action and a pattern of behavior.  When you have character, it eliminates getting your needs met by someone outside of the marriage, it eliminates lying and hiding behavior, it eliminates abusive behavior(think domestic violence and being controlling), and ultimately it eliminates the behaviors that are poison to a marriage. It is true that you can have relationships where one partner struggles with character flaws and yet when faced with the end of the relationship, I think that is when the strength of the character comes out and that person decides to change and grow.  But that change is obvious and overt and not just small micro actions that imitate change behavior.
When you have commitment and divorce is not an option, it drives people to work through what would be deal-breakers for others. I am in admiration of the couples that walked into my session and have done the hard work to heal a shattered marriage.  Marriages that often had no foundation to begin with and are struggling to overcome what has happened inside the marriage.  The power of commitment is a strong thing, it helps you to lean toward a spouse that has wounded you in deep ways and work towards healing and resolution.
When you start a relationship with character and commitment and you have character and find a person with character and you are both committed, marriage gets to be the easy end of hard.  I think that all marriages take work, but when there is a shared commitment and both choose to act in a way that honors each other, they can navigate the difficult situations life brings as a team and the challenges bring them closer, instead of dividing them.