My opinion on soul mates ...
Yes, I believe they exist.
I also believe they are people who sincerely love and care for each other to the point of working through each others difficult issues without bailing out. They grow together in similar directions and stay together. (If the relationship is built on a healthy basis, I like to see people stay together and work things out.)
I think many times the grass looks greener on the other side, and then people find, after a while, that "greener grass" was not all that.
Maybe I am a fairy tale butch. Though I am not in the market and am not looking around at the present, I do still believe in the existence of the type soul mates I described. Just for me, if I stopped believing it, I would become a very hard person. I am not there ... yet?