Wow…this is a very complicated question, lol! I will answer your question using myself and my dynamic…so this truly is my personal opinion.
I think people as a whole have either a dominate or submissive personality, no different than being an extrovert or introvert. I do not believe that this dictates whether someone would necessarily fail or succeed at being a Dominant or submissive in a D/s-M dynamic. I have a very dominant personality, but I chose to become my husband’s submissive. My husband also has a very dominant personality, but he had reservations about becoming my Dominant…at first. I don’t think our natural personality has anything to do with how successful we are or are not in our roles in our dynamic, rather, it is the level of effort and nurturing we put into a lifestyle that we’ve chosen. And just because I have a stronger personality, that doesn’t give me a pass to be a brat or use it as an excuse as to why I can’t submit to him. It also has a lot to do with trust. Both Dominant and submissive have to truly trust one another in order to fulfill their roles successfully. The topic isn’t as black and white being simplified down to personality traits to define respective roles. I enjoy being his submissive and he enjoys being my Dominant regardless of what others would “think I am”. It’s a choice.