I cross-dressed because I thought that clothes literally maketh the girl.
I just knew that I was a girl for as long as I can remember. Until I was 8 I did not know that boys and girls had different privates, although when I was about 4, my mother said that I was a boy because of my teeth. I really did think that it was only my clothes, hair and name that made me a boy, and that if I had long hair, a girl's name and above all, girls' clothes (and perhaps if I hid my teeth) there would be no difference at all between me and the other girls. At first my cross-dressing took the form of me walking around naked while wearing my mother's head scarf, or sometimes wearing a towel as a dress, but when I was older I liked to try on my mother's clothes.
Even when I got older, I felt stongly that girls' and womens' clothes confirmed that I was female. And isn't it great to twirl beautiful skirts? I didn't and don't care what I look like dressed as a male, but dressed as a female it was important for me to try to look beautiful. I lost much of that feeling in the last few years, but it's coming back now that life doesn't seem quite so hopeless.