If the comments are coming from outsiders, you are lucky to get their feedback. I assume it must be constructive. If you understand your "errors", practice write a couple of passages using that same concept. If you don't understand them, research until you do and make sure you fully understand.
It's funny, but I've been up to a lot lately, such as:
1) Working on writing some fiction with someone based off this idea for a story we both had.
IMHO, two writers can't write on the same work, especially in fiction writing. Each writer will use a slightly different "voice" and maybe a different cadence. The reader will likely pick up on the differences and be uncomfortable.
2) Serious article writing on Computing issues, which I'll get paid for
3) Generally writing for academic purposes, like university.
4) Writing for a website I'm working on. I guess you could call it business-style writing.
These all take entirely different approaches, but my lack of writing ability still shines through in whatever I do. Overall my writing isn't terrible, but I make glaring errors now and again and never realise until someone points it out, and those can be pretty fatal in certain situations (on job applications, for example). I was hoping to find a general guide on improving your writing, and hopefully the article mentioned will put me well on my way to actually being able to fulfil my plans.
I think you might be surprised how many times great writers rewrite. John Grisham's forst novel was so poorly written it was rejected a number of times. The publisher who finally brought it to market had to completely re-collate the manuscript .. shifting chapters, etc.
Most experts in writing will tell you, as Shyflower has mentioned, to put the work aside long enough to forget story lines, dialogue, etc .. then plan on coming back to it with a fresh approach.
I think one of my major problems is that I work in spurts. I can work under normal settings, but I get times when I am at my creative peak where the work just flows and I get thousands of words done in an hour. This rush usually leads to my downfall, as by the time I go back to rewrite I've already used that energy up doing that or something else.
You can't force good writing or creativity. Some days you are "off", pure and simple. One thing you might do to better utilize your time, when you're fiction creativity dwindles, switch to computer articles or other web articles.
Another problem most likely stems from the fact that I haven't received the best education throughout my life. I typically write how I would say something, and my speech isn't exactly great.
Are there any writing classes around your area? Also, look for informal writing clubs or groups. Few people can write really well without effort, study and practice. Some of us can't write really well even with effort, study and practice.
I would suggest that you find a well written article and read it in a normal manner. Put it aside, wait a day or so, then write an article on the same topic. Then compare the two. I'm sure you will see differences on how the original article "said" something and how you "said" the same thing. Repeat as necessary.
Another approach .. if your vision is lucrative enough, consider a ghost writer who can translate your ideas from concept to the written word.