Up until more recent times, and still true in some countries, marriage was a business arrangement often contracted between families to strengthen each politically or financially. The concept of romantic love was unrelated to permanent matings. Even where a couple didn't have parents pushing them into a marriage, more often considerations were can he provide a buggy to the family, does she know how to cook, and will they be good parents? Her being curvy or him having a washboard abdomen were not factors-- unless maybe for genetic.
Some of the idea that soul mate love and marriage go together has probably come via poetry, books and movies, but the dream for it is not recent and might be deeply imbedded. Jacob worked many years to marry the sister he most wanted (not that their marriage necessarily led to happiness) Then you have David. Was he smitten with Bathsheba for soul mate reasons or was it seeing her body nude in the moonlight as she conveniently bathed where he could see it? Was that soul mate love or lust?
Since I don't have answers for such questions, I will settle for simply explaining my understanding regarding soul mates and the ultimate (or potentially most disastrous) of such connections, twin flames/twin souls. There is quite a bit online and a lot of books out there to explain various author's understandings of the concepts, but I will settle for just giving the gist of what I have read and think personally is most likely to be true. And what I think might be wrong. Anyone who has experienced something different, please feel free to write extensively about it in comments. If your story is more lengthy than comments, put it in your own blog with a link here; or email me, and if it looks juicy enough, I'd be happy to post it here as another view.
If you don't believe in reincarnation, a soul mate is simply a person you feel a deep connection with and usually from the moment you meet them. They can be someone you work with and the two of you think so much alike. It can be romantic or friendship. Whether you believe in reincarnation or not, soul mates are not primarily about romance, sex or marriage but they can be.
If you believe in reincarnation, then these soul mate groups come together again and again and most likely began with their own creation (some say there are twelve in these groups). These may be family, friends and yes, mates. The relationships and gender might shift between lifetimes.
For reincarnation thinkers, there is another group of soul mates who repeatedly come together. I don't know if from creation but they are those with similar gifts and they incarnate in groups for purposes of political or artistic work. So you have the Ralph Waldo Emerson and the Concord, Massachusetts free-thinkers, who may have incarnated as a group many times in different creative patterns-- perhaps formed a new writer group in Montana this lifetime.
Could you have Hitler and his minions who may have done the same thing for negative reasons again and again? Soul mate patterns can be looked for in history and are fascinating to consider. Are you currently in one that is either good or not so good for you in this lifetime?
When the soul mate connection is romantic and sexual it doesn't automatically last for a lifetime. I have heard people say, when it breaks up, guess he wasn't my soul mate after all. I don't believe lasting forever is an indicator. A soul mate could come in and go back out of your life after fulfilling a purpose. You might have been wrong about him/her being a soul mate, but the fact that it didn't last doesn't tell you.
There are soul mate relationships which are karmic and temporary. They are intended to make right something from the past, teach you lessons you have managed to avoid so far, maybe finish business between two people which in reincarnation you don't get to walk away from. Some of these are very negative and the lesson is learning to walk away before you kill each other. There are soul mates who are intended to have certain children to raise them up, and once it's finished, they might go their separate ways.
Finally there is the term twin flame or twin soul which not all reincarnationists believe is true. This is the Adam and Eve story. Two created out of one. Shirley MacLaine describes how that works in her book, 'The Camino.' Twin souls are two halves of the same whole and the draw between them is very strong. Are they always meant to be together sexually in each lifetime? I don't think so. If they are together is the relationship nirvana on earth? Again I don't believe so.
The same friend who told me the story of the hawks also told me that when twin souls come together who are not evenly matched for energy, instead of the most romantic, beautiful relationship you could imagine, it can be very destructive. Yes, when they are evenly matched, it'd be the best mated relationship two people could experience; but there's that 'if' and it's a big one.
If you had a soul mate relationship with someone which worked out disastrously, my advice would be to do all you can to become the person you believe you were born to be. Work on being personally stronger, and the next relationship will reflect it. This works, of course, even if you don't believe in reincarnation or soul mates.
On the one hand, what you believe about soul mates is pretty much irrelevant. You can obviously find good relationships and be happy without having them defined spiritually. But then there is that other hand where if you do believe in them and spend your life looking for that perfect soul mate romance, the belief could be destructive and cost you a lot of good relationships along the way. Not to mention your soul mate, if you do come together, isn't likely to be perfect either-- given that would take two perfect people to make happen. Ever seen that?
(The sculpture pictured here is mine, titled Soul Mates. It is fired clay, weighs about 75 lbs, is 29"L and 22" H. I did it about eight years ago and had thought I would put it on its own stand, but the living room doesn't have that kind of space; so it generally has ended up the piano-- except when it's carried outside for photographs.
I don't do sculpture currently for the very reason that Soul Mates demonstrates-- what do you do with that many little people? Unfortunately clay sculptures that look like bronzes didn't end up being in demand in galleries. The clientele wanted bronzes and I liked best working in clay-- not to mention the huge investment in doing a bronze that still might not sell.)