I suspect we are all in the process of becoming what we wish to be and at the same time, exactly what we aren't.
Which is to say: when it comes to identity and position, it is equally possible to be ourselves and something else. Even if the two seem contradictory.
Without excessive exposition; the place of the sub or slave is inherently one of servitude, to a degree. And yet it is precisely in that willingness to adopt that position that they grow, learn and advance themselves through thier dedication. They master aspects of themselves and perhaps life.
Conversely, it can be said that the identity of dom or master is entirely dependant on the willingness of another to submit to them. They have power over people but only under conditions that are agreed upon. In this way, they are bound.
Through this, the connections between what we are and what we aren't may be made clearer.
Considering these before starting a relationship is key, I think.