Get Synched and Write On!
I would like to be able to tell you exactly how to achieve a synchrony of
left-structure
with right-flow in your writing. I can't, of course. No magic blender exists.
Good news, though. The balance of structure and form in synch need not be 50/50
for writing to ring true. Of course
it doesn't—who could balance that? But it does need both of these. You could think of them as Right Seine and Left Bank—They go together like horse and carriage.
What can you do to attain this wholesome (pun intended)
state of writing out of your mind?
For starters, what you need is a Top-5 List of what to avoid when you start writing seriously.
Here is that list:

Warning. This is a sampling of ways not to write, a taste of the worst offenses. Beneath a shimmering surface that we will barely disturb lurk denizens of deeper realms. These gaucheries and pratfalls will be trapped, scrutinized, tamed, and released on a regular basis.
Contact me to suggest your own suspects.
Avoid passive constructions, strenuously
Active voice means that the subject of the sentence performed the action:
You ate it.
You is subject, ate is verb, it is agent receiving
action. The subject acted upon something.
Passive voice means that the subject received the action:
It was eaten by you.
It, the subject, is acted (or eaten) upon.
Using the passive voice can cause the reader to feel that she is being addressed
from something out in the void:
It was decided that we no longer need your services.
Who decided? (And she might well wonder why.)
Strive to use the active voice when you can and it fits. It is more direct
and forceful, and often it is more economical (read shorter: I love you
versus You are loved by me).
It is not always apt, using the active voice, but it very often
is. Just ddon't let it construct you.
What else can you do to avoid common writing pitfalls?

Don't bloviate
Never in public, you say? Actually, what the word means is to orate verbosely—too
long too much. Officialese is full of it, in more ways than one.
The fact of the matter is . . .
Those words serve no purpose other than using space. No, they serve one
other purpose: They make the writer sound like a pompous ass. That phrase
is a member in good standing of the club of useless constructions. (Can
you tell that I once worked in a law firm?)
Worried your paper won't be long enough?
Then get more data. Don't try to fill it with unnecessary and uninteresting
over-wording. Your bloviation will be noticed and disdained as much as that
first thing you thought of that we never do in public.

Knowing your Audience (your reader) Enables you to Speak Directly to Her, Him, It, or Them
This involves not only using the active voice but also aiming to the level
of your audience.
If you are writing an article to be published in a medical journal your
level of discourse will be very different from that of writing to your peers
(even if you are a medical person you would likely be more casual
with peers than in the former, more formal, instance).

Have supporting evidence for whatever you aver
If you aren't sure, either look it up or don't put it in. Or at least make
it clear that your information is uncertain.
The funny thing is, the blogging rage currently among us seems if anything,
at least from my limited sightseeing, to be sharpening peoples' writing
skills. If they can't make themselves understood they won't be read, or
they might be flamed (if bloggers can validly undergo such punishment).

On tidying
I don't envy people in the days before word processors and, worse yet,
writers without access to printing presses. Consider the drafting of the
US Constitution. How many sheets of paper did they go through? We are so
fortunate now, simply correcting at will.
There is no excuse not to correct your work.
You're right; that is a passive construction. They are not always ill-chosen, but in this case let me put it more directly:
You
have no excuse not to correct your work.
No matter how accomplished, everybody needs practice to perfect a written
piece. That's the purpose of the first draft. Get something down now, and
make it better later. No writing with any serious intent behind it should
go out without at least one editing first.
Especially if you have trouble proofreading your own work, and even if you
don't, first let it "cool"—wait at least an hour, maybe a week, before looking
again. When you do so, look at it first with a critical eye, searching for
error—spelling and punctuation, mainly.
When you have done that, let it cool again a bit before returning. This
time, as a disinterested reader might, read for meaning. Hear your words.
If it's important and you're having trouble, button-hole a listener. What
does Heidi think you mean? How would you tell her? Quick—Write that down!
One last point about proofing: Don't rely slavishly on the spell-checker.
Use it, certainly, but be aware that it has given this blooper a free pass:
Many find it difficult to edit there own words.
The above points may seem inconsequential, but if you weave them into your
writing your readers will read a difference. You will have more confidence
in your writing and, with more confidence, you will relax.
And do you know what will be happening then? Structure will start to meet
Flow, and you will be closer to writing out of your mind.