S.W.
My daughter is 10 now and is starting to develop breasts and show other signs of puberty. We have had several talks about growing up where she ends up in tears, telling me that being a grown-up is no fun, that she wants to be a kid, that she doesn't want to have to wear a bra and deal with periods, etc. It's not that she isn't mainly a very happy kid, because she is. But she is smart enough to see that being a grown-up comes with more work and responsibility, and worry. These talks have concerned me some. I do my best to reassure her that growing up comes with some good stuff, too.
I don't remember being open enough with my mother to tell her these things, but I did suffer from an eating disorder throughout my teen years. One thing anorexia does is stop your periods and stop any further sexual development. Even though anorexia was not a well-known disorder back in the 1970s and my small-town doctor never could figure out what was wrong with me, somehow I just knew that if I didn't eat, my periods would not come and I wouldn't have to face "grown-up" things.
I think we sometimes stress "you're such a big girl/boy!" and "look how big you're getting" a little too much.