Quote from Wordmaker:
It's okay for your first draft to suck. In fact, it's almost better if you think it does, because you'll be more open to making changes. The important thing is to first get the book written.
This, so very much. Personal computers make it a breeze, too. The first complete full-length fiction I wrote was typed up manually and got covered with so many scribblings, cross-outs, and revisions that I doubt anyone else could have understood it. Also, aping someone else's style is a natural part of the learning process, as Stephen King points out in
On Writing (one of the best resources I've ever read on the subject, BTW) but if you keep at it, eventually your own style will start to emerge.
Like the Deposed King, I'm self-published. I've had no formal training apart from your basic English courses, but I've been reading and writing most of my life--pretty much as long as I've known how--and while I couldn't diagram a sentence to save my life, I know the rules of grammar and have a pretty good grasp of what works in a particular context and what doesn't.
Keep writing. Keep reading--good books, so you have something to aspire to, and bad ones, so you know what
not to do. Listen to real people talk, in real life. Experience stuff. Do your research.