The period of time before transition was surreal. I was keenly aware that there was a part of my brain that needed me to be a woman, and that it was "not like" the part of my brain that had ideas, made choices, evaluated, and analyzed. I couldn't reason with it, couldn't understand it, could only listen to it. It wouldn't leave me alone. Another friend from this site and I came up with the phrase "Gender Identity Preoccupation" to describe that phase.
I've never had that experience before or since - that there is a part of my brain that is sending messages that are at odds with what I might have chosen or decided.