The couples I see that fall apart complain about each other behind each other's backs to their friends. They're snarky, disrespectful, when they fight they fight dirty. When they get resentful they retaliate instead of talking.
Just. Be decent. Like each other.
It's not that hard if you can work on not being selfish, self-centered, or self-righteous.
Or rather hardtimes(financial, illness, children, etc) can change the person you once 'liked' into someone you may not.
The things I've heard people say about, or worse, to their spouses sometimes stretches my definition of basic human decency.
Regardless of how someone changes, every person deserves basic respect. Even little things like complaining about bad habits behind a person's back fosters resentment borne of disrespect, resentment that can grow and fester. Resisting that urge and instead treating ones partner with dignity is a critical skill many couples lack.
The stigma against divorce (made worse when driven by religious edict) is often why things turn into the bad state of affairs you describe: spouses treating each other as adversaries, speaking about them negatively behind each other's backs, etc. If you get to the point where you don't like your spouse anymore, just get a divorce. No, that's not a decision that should be made lightly, but unless you have a really good reason to stay in a relationship that makes both parties unhappy, it's crazy to stay together.
I doubt the stigma of divorce has any such impact. Plenty of second marriages contain hatred, anger, resentment, etc
Was there significantly more abuse etc when divorce was more heavily stigmatised?
You should just live together for a few years first then.