So... This is where I get writer's block...
WazDakka and I started out in a vanilla relationship. Sure there was pretty much always some BDSM play there as it was a pre-existing interest for the both of us, but the relationship itself functioned in a vanilla manner, as boyfriend/girlfriend with little - to - no power dynamic.
Then, a while ago, it became a lot more D/s (Dominant/submissive). A power dynamic definitely came into play and was, in time, recognised. It fit, and wasn't an especially thought-out thing. In some ways, it helped that there was never a power struggle or difficulty working out where the balance was as WazDakka is Dom through and through, as much as I am sub through and through.
Lately though, it really became clear that M/s (Master/slave) was much closer a description to how we were actually living. WazDakka pointed this out and since then, we've effectively relabelled our relationship. I'm finding myself behaving differently too, actually. There are times when I remember my behaviour is a reflection on my Master and as such my conduct should be the best it can be.
There have been a lot of small shifts recently, and all for the better. I can only look forward to what the future has to bring for us :)