I'm a switch.
You might not think so, but I really am. And in my mind, seen over a long time, it's fairly 50/50.
In reality, at least in the last five years or so, I've been 100% dominant. And although I occationally feel the desire to submit, to play with that side of me, most of the time it doesn't bother me.
In my mind, I have a mental "container" that needs to be filled with BDSM regularly. If I don't get BDSM, I'll survive but my life gets more boring and bland. I really feel the lack. However, both dominance and submission fits into that container. I don't need both, all the time, I just need SOME form of BDSM. So as long as I "get my fill", it doesn't matter if I do it has a submissive or as a dominant.
I enjoy different things when I'm a sub versus when I'm a dom. Power, however, is a common theme. I enjoy playing with power, who's really in controll etc. Also, it's all about the sub. Always. I enjoy pleasing the sub (or get pleasure, if the sub is me). This "guilt free" pleasure is one of the best things with BDSM, in my opinion. By that, I mean that the sub doesn't get any other choice. He/she can't reciprocate, and isn't expected to. And so there is no feeling of "I should be doing X, Y and Z" or "Does she think I'm too passive now..?". No insecurity, just pleasure.
And that's probably what I miss the most, when I'm just a dom and never a sub. As a sub, I could just lean back and recieve. I knew it would be all about me. And I knew the dom would enjoy it too. But most of the time, the rush of power when I strap someone in and tell them exactly what I'm going to do to them.. That rush is so great, and it's such a great turn on, being a sub is the furthest from my mind.
Like I said, it's all about power. When I'm the dom, I love manipulating the sub. Putting him in the state of mind that I want, making him horney or apprehensive or scared even. Turning him on, knowing how "high" the rush is taking him and mixing up all the right ingredients to get the result I want. It's like playing a piano, with the sub as the instrument. Or cooking, adding a hint of that and a splash of that, and leaving it to bake for juuuust long enough.
So yeah, that's what BDSM is to me. That's what I love about it, who I am, how I define myself. In a somewhat rambling and disjointed manner. :P