Writes non-fiction author and editor Verlyn Klinkenborg in his insightful new book Several Short Sentences About Writing (Knopf, 2012), page 67:

Your job as a writer is making sentences.
Your other jobs include fixing sentences, killing sentences, and arranging sentences.
If this is the case — making, fixing, killing, arranging — how can your writing possibly flow?
It can’t.

Flow is something the reader experiences, not the writer.

A writer may write painstakingly,
Assembling the work slowly, like a mosaic,
Fitting and refitting sentences and paragraphs over the years.
And yet to the reader the writing may seem to flow.

The reader’s experience of your prose has nothing to do with how hard or easy it was for you to make.
You’re not writing for a reader in the mirror whose psychological state reflects your own.
You have only your own working world to consider.
The reader reads in another world entirely.