I don't know much about writing, but the one, and hardest, lesson I've learned was the art of not writing.
It can be contradictory, obviously, but understanding what not to write is the one fundamental skill often overlooked that leads to nothing but the demise of the object and subject, reader and writer.
For the writer, there is no abstract analysis, a "simple poem" describing one's feeling, or a crazy non-sensical novel: every written word is a promissory note with one's future self.
Writing is not simply describing what has become, or hypothesize on becoming itself or other abstract idea.
Writing is the unraveling of becoming itself - the set of directions with whom the subject will become.
This may appear as a fantastic, beautiful idea: setting up one's steps to become a better being. Yet, it can easily become the most destructive of forces.
Whenever melancholy, tragedy, evil, darkness shows up, there also exists an appetite for the writing of such experiences. The writer, naively, wants to merely "take out of the chest", describe what's happening, find a language for one's sufferring. The problem is there's not way of doing so. In each written sentence, the writer becomes the future subject, when not prisoner, of his own words.
Closely analyzing Nietzsche's last moments, and myriad similar examples, it becomes clear that they are not merely oppressed by an external societal force, inasmuch as they're also strong prisoners of their own literary becoming.
A more disturbing analogy would be Plato's claim that that poets should be thrown out of the city and the historical proof of this. From Milošević to German's Reich, the unraveling of the vicious national identity only happened through the medium of poetry, or associated means.
Surely, most of these writers did not actively conspired to turn literary hate, bias, and "will" into murdoreous, evil behaviour; still, the subject of such activities were surely motivated, when not urged, by them.
Writing is the most powerful tool in the world. And it wouldn't be surprise if it were dangerous.
That's why for me, I only write what I want to become, to see and to experience.
And if I try it, it's for a good reason: all good books are catholic books.