99% of passing is attitude. Which basically boils down to if you don't love yourself, how can others? If you can accept yourself with all you great points, and all the lesser points? How can others?
Transition starts from the inside, not outside. I had 2 failed transition experiments in my early 20's thanks, in large part, to not coming to accept me as me. I'm still that 6ft tall big everything person I was with no hop of passing, yet.....