The Worst That Can Happen
What's the worst that can happen to your marriage? I think it is a build-up of resentment.
It is next-to-impossible to show love to someone when you resent what they've done or not done. Even if you try, your actions will be suspect. Your body language will give you away.
Resentment is what allows the thought process that justifies emotional affairs, infidelity, and deliberate overspending or overeating.
Resentment is what leads to badmouthing your life partner to your family and your friends. In long lasting marriages, spouses speak even better of each other than their friends do.
How can you get rid of resentment in your marriage? Find Third Alternatives to your disagreements, Expect Love and drop the rest of your expectations, and Assume Love while you consider alternate explanations for the stuff that bugs you.
Or you can sit and simmer until your spouse or life partner falls madly in love with this miserable, seething version of you and chooses to do everything you expect a life partner ought to do.