What an excellent question/topic, Lily.
I think its also interesting, (though not all together indicative) to learn what line of work dominants and submissives find themselves involved in.
Me, I have only recently began embracing my dominant side in my relationship. In my personal life, I have always tended to be very outgoing and dynamic so it is not such a stretch for me. But I was brought up to be a "nice" girland for years I bought into that line of crap that nice girls aren't supposed to be demanding, assertive or embrace a darker side of their personality. Career-wise, I work in a "helping profession"...and I am comfortable with being compassionate, giving and something of a mentor to those I work with. Initally, those traits would strike me as submissive, but I find that these traits are very complimentary when I use them in a dominant capacity.
I do think that being dominant in my relationship has taught me to be more confident and helps to balance me out though. I think it would be draining to be "all domme, all the time"- in every possible facet of my life.
Hope this gives some further insights!