"Before you get married, your relationship must have trust. That means when he goes out with the guys, you're not gossiping to the girls about what he could be doing you already know"
The ability to fight fair
Conflict is a natural part of all relationships, but the key to healthy conflict is in how you treat each other when you're at odds. How you fight now is a rather accurate predictor of how or if you'll resolve conflict in the future.
If you and your partner handle conflict consistently in a destructive manner like screaming, interrupting, yelling or calling the other names studies show that you are more than twice as likely to divorce over time.
A good relationship is where you handle the conflict constructively: you fight fair, know when to engage in an argument and when to let it go without resentment, don't name call, validate each other's feelings, and calm down when you talk.
Lots and lots of trust
Before you get married, your relationship must have trust. That means when he goes out with the guys, you're not gossiping to the girls about what he could be doing you already know. You should feel safe and secure that the person you're preparing to spend your life with has your back and will honor the commitment. Trust is essential without it, it's like walking a high wire without a safety net."
Love for your partner at his or her worst
The most important thing before getting married is to spend enough time, and communicate deeply enough with your partner to see their fears, insecurities, challenges, addictions, temper, mental health issues, regrets, shame, and all of the qualities that make up their shadow side.
As time goes by with crying newborn babies, sleepless nights, the flu, financial troubles, work stress, and inevitably people letting each other down that shadow is going to rear it's ugly head. It's imperative to know that you can stand by each other when you're not your best selves. Know each other's faults, and be able to accept them. That is what you need to know before you walk down the aisle.
You don't have to talk nonstop, but you do have to let it all out when you get chatty. There needs to be fluid communication. So marriages go sour simply because the couple doesn't know how to talk things through and resolve arguments without it escalating.
You should be together long enough before getting married to have had at least one major disagreement and prove that you two are able to work it out successfully.