It's very tempting for me to believe in a lot of this "idealistic" stuff because it's just so nice but the idea of a unique soul mate just doesn't seem quite right to me. Life seems too diverse and there appear to be too many people out there that I could make unique, amazing connections with given the right circumstance (which is clearly vital). There are undoubtedly a group of people who we're each capable of clicking with more than others, I just don't feel as though there is one person for everyone.
I feel like I'd be setting myself up for a world of pain if I didn't try to move with the ebb and flow of life, being grateful for each interesting person I meet and being aware that life isn't perfect so relationships, love and marriage are unlikely to be either. You just can't build this picture up in your mind of a partner who personifies perfection and absolute union. Whether that person exists or not is almost irrelevant, you need to live in the moment and do away with any pre conceived ideas, how do you feel inside, now, as you're in their presence, that's all that matters. (The danger here is losing a sense of perspective, love is blind anyone?)
Also, ideal partners should form a great double act, balance is everything. Given how we can all better ourselves in certain areas and how we're all lacking in others, husbands/wives should be people with who we are best suited to attaining a kinder, more loving, balanced nature. So again, given the diverse nature of, for example, myself and the people I come across, I feel one person might subtly channel me in one direction while another person with differing qualities might another etc. There isn't necessarily a better or worse path if they're both essentially "good".
Just a few thoughts anyway, not sure how well they flow with what's been said above now.