It has to do with how you perceive a relationship ought to be, and whether you try to move in that direction at all times.
Imagine that you’re having an argument. At any point, you can say or do things that make it worse, that you will regret the next day (or maybe forever), or you can go in another direction. I’m not talking about mollifying your partner or avoiding hard truths. Sometimes they have to be said, as things cannot move on without them being expressed, but these are not the kind of words that are regretted the next day, because they are truths.
But it’s not just with events of disagreement that you should intend for the relationship to be good; this should be your daily practice. It is the difference between driving hands-off and steering the vehicle. What does a good relationship mean to you? Steer towards it.
We’re not talking here about major production; no weekends in Paris are called for. Small changes alone suffice to make a difference; each positive event creates a positive response, and the relationship can take an entirely different course, just as surely as the opposite exchange of negative responses spiral into disaster.
So don’t just hope that your relationship is good; make the choice that it will be so.