They do it regularly: with self discipline and dedication.
I may not be one of best writers around, but I've got dedication and self discipline (which comes from motivation, because I love what I do - although it's very hard work). I try to have fun, whilst I try to earn a living.
Top writers WRITE AND REWRITE - many times over, so words flow better each time.
They aim for perfection - very, very hard to achieve; although one can always improve.
Every time I go through a manuscript, I change things (like repetitive words, incorrect grammar and punctuation) to try to get words to flow better... but one has to draw a halt somewhere, otherwise my books would never get published.
HOW TO AVOID COMMON MISTAKES What do you think are most common mistakes of new writers?
Take a coffee break while you do this short assignment.
My immediate thoughts:
using too many words
The art of good writing, I believe lies in brevity, so omit all unnecessary words.