It makes me sad when I have a couple that comes to me for counseling in crisis, when the relationship is already in its death throes. People come in seeking a panacea to all the years of damage to their relationship, but unfortunately, I am not a magician. Counseling cannot be a last ditch effort, because if one partner has already checked out, there are not enough hands on deck to do the work.
The thing I can't really tell them, because it won't be helpful now, is this: your relationship probably could have been saved anytime before now, if only you had learned to really communicate with each other. Yes, I know that *everything* isn't about communication, but if you can't do that part, the other stuff is always going to fall apart. Conflict is a natural part of any intimate relationship, and to avoid it entirely is counterproductive. There will be times when you will be unhappy in your relationship or upset with something your partner is doing or not doing. But learning to do conflict well is a key function of communication. Being able to look at your partner's face and say "this is what I need" or "this is how i feel" is the fundamental building block of a strong relationship. This is a skill worth learning at any time; if nothing else, you'll know it for next time.
So when a couple comes in and I can clearly see where their disconnect is and it is a glaring lack of understanding of one another's basic ways of being in the world, I will never tell them it's too late. Even while it's a long shot, I will take a deep breath and dive in and do my best. But to help them navigate the unfamiliar territories of vulnerability, honesty, intimacy, etc etc, when they've been living elsewhere for years, can be scary and difficult for them. It is amazing what people don't know about each other even after having been married for 5, 10, 15 years. So we start with communication. If I had a dollar for every time I say to a client "You have to actually USE WORDS", I would have enough dollars to go on a nice vacation.
So my conclusion here is: learn to use words. If you're in a relationship, the best thing you can do is communicate authentically with your partner. If you're not in a relationship, practice with the other people in your life so that when you are, you will know how to do this. Relationships are always going to be challenging, but if you learn to communicate and to do conflict well, you're much better equipped to handle all the other stuff that will arise.