We engage two completely different aspects of the mind when we write: the Creator and the Editor. Master the proper use of both, or writing will bring you a lifetime of unnecessary suffering.
The Creator is the childlike and creative part of our mind. It's the part that brainstorms, joining together weird or seemingly inconsistent ideas. It dreams up vivid images and themes. And it makes us cringe with its honesty and its willingness to tackle difficult, embarrassing--even explicit--subjects.
The problem is, much of what the Creator creates is pure crap.
Indulge your Creator, don't judge it. Give it free reign to create all the crap it wants, because every so often, hidden in all that crap, will be a truly brilliant idea.
The Editor is the adult part of the mind. It corrects, adjusts and tweaks things. It selects the right word. It polishes phrases, sentences and arguments. It takes the things the Creator creates and improves them.
Unfortunately, the Editor also takes the things the Creator creates and says things like no, don't say that, that's stupid. And that part of the Editor is fatal. Nothing murders creativity more efficiently than hearing your own mind say what you just thought up was stupid.
All of our struggles with writing derive from engaging the Editor before its time. Recognize that when you are in pure creative mode you'll need to protect your Creator from interference. Shut your Editor up and stop it from judging, so your Creator can feel confident and comfortable enough to let your ideas flow--yes, even the really dumb ideas.
Make your Editor wait. The Editor must come second to the Creator.