What Relationship Facts Should Everyone Know Before Getting Married?

I heard an advice before getting married. It was specific to women in heterosexual relationships, but very helpful. She said, Pay attention to how he behaves when a woman tells him no or scolds him. Not his mother. Not someone he is very close to. But see how he behaves with her, because that will one day be you. Will he be understanding and accepting? Condescending and rude? Open to compromise? Demanding? And similarly, for any person of any gender, see how they treat those who cannot benefit them. Everyone will be nice to their boss, to the person they're pursuing, to someone who holds power over them. But how do they treat restaurant workers? Random people on the bus? Animals? Pay attention.