The best piece of advice relationships counselors will give you is to learn to communicate effectively with each other. If you master the art of communication then everything else will follow. You will wonder at just how easy everything else becomes when you give each other carte blanche to say what ever needs to be said.
Just as long as the communication between you stays respectful. Say what needs to be said but do not be mean, nasty, or cruel. That's not communication, that's abuse. If something happens in your relationship that makes you mad then tell your spouse that you are mad but that instead of going off half-cocked, you want to take some time to organize your thoughts and figure out the best way to approach things.
Then, when given enough time, you can calm down and look at things rationally and come back to the discussion with a fresh set of eyes. Anger is blinding and when you are angry nothing can be accomplished to the positive. If the anger stems from something that was hurtful, it is human nature, I think, to want to hurt right back. If this should happen then take my advice relationships can't survive if one of you is always pitted against the other one.
Sometimes fighting can be a good productive thing to do. But, if it is a constant thing in your relationship then it will wear down the love and the relationship will not survive. Pick and choose which hills you want to die on and which ones you don't. If the fight is about how one betrayed the other then this needs to happen. If it is a fight about the toilet seat being left up, then, not so much.
Most of the time, the mistakes we make are just that, mistakes. Not intentional hurts but still they hurt anyway. If you are the one who has done the hurting, then apologize as soon as you can and as sincerely as you can. a sincere apology will go a long way to fixing a lot of things. Ask what you can do to make it better.
Keep the romance alive. Do things together and do things apart. Quality time can be described both ways. Spending time together is fine but, there is such a thing as too much of a good thing. Spending all of your time together is just not healthy. So, spend some quality time apart too. This way you will always have something to talk about and new stories to tell.
If you find that life is getting in the way of the two of you finding time to spend together then it would be a good thing to do to set aside some time every week and plan to spend that time together. Go have dinner, see a movie, just take a walk down by the river. It doesn't matter what it is just as long as you are doing it together. If nothing else then to just remember each other's names.
With this advice relationships may have a better chance of survival and neither of you will ever go to bed angry.