This is going to sound very new age, and trust me I am not. But something I found a bunch of years ago is called anam cara. This idea of a soul mate is relatively limited and I could never relate (I was as vehement as you are). After diving into myself and doing craptastic amount of research I found something called Anam Cara. It fit with both my spirituality and with my belief that there is not a mythical ONE!
Its an interesting read if you can find a site that isn't all lovey dovey (unfortunately, on the web today it has been taken over from fact and given over to more myth). The gist is, Anam Cara is a soul friend or like soul. You meet many soul friends in your life that make connections with you, create an impact on something. Sometimes they stick around sometimes the connection ends. But the impact is no less important to your life.
Just something to consider, seeing as I also don't believe in soul mate but wanted to understand what the hell people were talking about.