Self-acceptance was the biggest challenge for me, as most everyone has mentioned already. Though for me, I had a hard time doing that until I realized that I already had good friends who were accepting me as I am. Once I understood that, I started to realize I had been holding myself back the whole time. If I just be myself, then the people who matter to me will stay by my side. Just reaching that point of being comfortable with my identity lifted a tremendous burden from my shoulders, and suddenly the rest of the world didn't seem as intimidating.
To be fair though, I've probably been having a somewhat easier time crossing between gender-spaces than most people would. Passing and outside acceptance were my major fears until I began to accept myself.
~Kaitlyn