You always need a mission to write and at the same time you must have an imagery audience.  It is that audience which gives your writing focus.  It is striving to reach them which will give you the words you need to complete your mission.

The words necessary to reach your audience will come if you know why you are writing.  You may not know how to get there but the words will materialize as you make your journey.

Your only job when you are complete with this leg of the journey is not to confuse the reader and take out everything that gets in the way.  If you can still delete your passage  and your writing stands it was not necessary.

You always need a mission to write and that always comes first.    Know why you are writing.  And to whom.  The words always follow.  They do not come first but are always last.  Start with your mission.