A LOT of BDSM stories out there seem to have a heavy dose of "romantic love" to go along with them. I suppose it makes them easier to swallow for a wider range of people. I read them and I enjoy them but I understand that this is NOT always the reality.
I don't know much about past-lives or old souls being reborn or anything of that nature...but perhaps you write those storylines because it's what you're wishing for in your own life. A harsh/stern but loving mistress who will be exactly what you need her to be.