Unfortunately, the AWA section is not a reflection of whether or not you're a good writer. It sounds harsh to say so, but it's solely a reflection on whether or not you can write IN THE WAY THEY WANT YOU TO WRITE.
That means you have to know the structure inside and out, and just adapt that format to whatever the passage is they give you. I've spent a bunch of hours with Greenlight's free AWA videos: http://greenlighttestprep.com/module/gre-analytical-writing
I don't think my writing is any better, but I KNOW that my AWA section is waaaaaaaay better. Practice makes perfect, but the benefit of knowing how to write in the way they want you to write is that my practice essays are easier. I know what to do right away, and don't freeze up the way I did the first time.