I was really scared of turning 18 because I thought that it would mean being expected to act differently, or have to be more grown up, and in a way I was right but not in a bad way at all. I found that it gives me the freedom to act however I want, and if anyone has any problem with it then I don't care, because I am an adult, and I can live my own life however I choose. It's also really nice to not feel restricted in terms of getting in to places, buying alcohol, not needing parental permission for things, etc. Not that I even particularly want to do the first two, it just feels nice somehow to know that I am legally allowed to be free, go anywhere, do anything, BUT at the same time young enough to be protected by my family and act childlike if I want to.
I have also grown up immensely, and unexpectedly, in the past year or so. I don't even mind not being a kid any more, which I never thought I would say.