The most important thing in writing, according to people who write about writing, is finding your inner voice. (The most important thing in writing about writing is telling other people to find their inner voices. (The grammar is ambiguous, but for clarity it's usually one voice per person.))
I too believe that finding one's own voice and style is important. But it is eternally at odds with how we learn language. We pick up bits and pieces in voice and in print and we repeat the patterns. Originality is just finding new ways to say things with old material. Even when I'm rearranging the bits, there still exists something of the original author's feeling, or at least the feeling I got from reading the words. Am I just a creative plagiarist?
I started out by stealing from Dave Barry - not just his style, but also specific jokes. I'm not sure if I regret that or not. I think I needed training wheels in the beginning. Bob Frost teaches painting by getting people to paint what he's painting. I wonder if writing would benefit from more of that sort of guidance.
I've plagiarized - in grade 5 or 6, I was supposed to tell a scary story, and I basically stole a story from a library book but wrote myself into the story. (Someone else in the class who'd read the same book recognized the story. I lied and mantained it was a coincidence.) If you think about it, doing something like this, above board, could be a very useful exercise. Just pick a story and write yourself into it. It might only be interesting to you, but it's good practise.
We look down upon fan fiction because the author didn't exclusively use original characters. Even when the books are licenced and published, they might still be non-canon in the timeline of the universe they use (Star Trek books, for example). In grades 10-11, I wrote a Nintendo fan fiction piece - perhaps inspired by a bizarre Sailor Moon / Star Trek crossover I'd started to read, making me subconciously realize that this was something I could do. You wouldn't want to read it unless you were my mother. But it felt really good to write and I believe it was good pract - no, wait, I ended the last paragraph that way.
How far can this idea be extended? Should you learn comedy by telling other people's jokes? Kids will do that unashamedly. When we go to a bar and there's a band, often it's a "cover band", but they sound good in part because they pick and choose the best songs from the popular music canon.
I like to think that I go out of my way to be original, but even to go out of one's way is a canned phrase (and one of my favourites). So is the idea of some person or persons liking to think something. I think we should recognize the opposing pulls of the urge to copy something good and the urge to be uniquely good. On some level, we are always doing both. (Unless you just e-copied the whole paper and stuck your name on it. That doesn't even merit the dignity of "copying".)
What would writing be like if we didn't all have to reinvent the wheel? (Bill Watterson expressed a related thought, about cartooning, in his Calvin and Hobbes Tenth Anniversary Book. I really only changed one word. Would it be dishonest for me not to admit this? In the past I would normally not disclose. I think there was a certain merit to not doing so - this dislosure has taken all the gravitas out of the end of this note.)