Growing up, I learned that the standard for a successful romantic relationship was simple: He asks you to marry him. Get hitched, have kids, buy a house... etc. The be all and end all of mainstream monogamous pairing.
Of course, this doesn't work for everybody. Besides which, it's ridiculous; obviously marriage has nothing to do with whether a relationship is successful or not (except for folks who want to cap off their successful relationship with marriage). But when you take away marriage as a necessary result, or sign of, a successful relationship... what do you use to gauge the success of your romantic relationships?
I have been working this out for myself in the last few days, and I'm very interested in what you think, too!
As someone whose marriage ended up not working, I don't think marriage is a good barometer of success even for so-called traditional relationships. So, what is?
First, it's important to remember that all relationships are dynamic, as are all people. Your "successful" year-old relationship will be different from your "successful" ten-year-old relationship, even if it's with the same person, and even if it isn't romantic in nature.
So the question isn't "Have we reached success?" but "Is this relationship fulfilling its purpose?" Relationships of all types have some sort of purpose, whether it's companionship, business partnership, child rearing, sex, some combination of these, or something else entirely. They are also not time-limited. You can have a successful relationship that lasts just a few days, or one that is never successful but persists for years.
Ask yourself, "What is it that I want from this relationship?" Are you getting it? If the answer is yes, then ask yourself, "What is it that the other person in this relationship wants from it?" Are they also getting that? Then your relationship is successful.
It's vital that you continue to ask these questions of yourself and each other, to ensure you both (or all) continue to get your needs met. If ever the answer is no, you must decide whether the relationship can be salvaged and if you are willing to do that, or if it's better to end things.
I'm reminded strongly here of when I first met Marty. I was hesitant about dating someone who was polyamorous (ha!) but considered my situation. I wasn't committed to anyone, so I wasn't worried about damaging any other relationships by dating someone who dates other people. I was also mostly concerned at that time with meeting people, building connections, and enjoying time with people who made me happy. I considered whether being with Marty fit these criteria, and the answer was, resoundingly, yes. Whenever I was with him, I had a great time. Through him, I was meeting people I enjoyed being with. Because of him, I was learning to challenge my ideas about relationships. And it didn't hurt that I found him incredibly sexy. So I decided to keep seeing him until that stopped working.
Since I made that decision, things with Marty have continued to work (sometimes, admittedly, better than others). Certainly, at this point what I need from that relationship is dramatically different from what I needed from it when it was a week old. A successful third date typically looks nothing like a successful anniversary, after all.
But this is an ongoing process, if not always a conscious one. Keep questioning whether you're getting what you need from each of your relationships. If your needs change, expect your relationships to change. The same is true if your partners' needs change. Should you move from friends to lovers? Coworkers to friends? Lovers to acquaintances?
And there's no need to regard a relationship that has ended as a failure. Perhaps you are more successful in your current roles than your previous ones (say, if you went from lovers to friends). In fact, many romantic entanglements end this way, with both parties being better friends than they ever were lovers or spouses. This is not a sign of failure, but of a change in needs. As lovers, they didn't fulfill each other's needs. As friends, they do. Success!