Bleh. Do I have to copy art in order to become better?

I've been drawing since I was 4, and I've never, ever copied art. (I would say I am above average for a 14-year-old.) I have decent anatomy skills. I can draw poses that don't include that much foreshortening. I am having trouble with foreshortening, however. I am working on it. I've found through looking at my previous works that I do have a rather fast rate of improvement. If you look at art from two years back, there is an extremely conspicuous difference. However, I never copy images. I find it to be a rather tedious activity. I just tend to draw whatever pose comes to my mind and just ....draw it. I am kind of hoping that my anatomy skills just develop on its down, without me copying images. Perhaps just practice? Or is it an essential tool of mastery? (Of course, I won't copy, unless it is really, really an ingredient to mastery.) Help?