It is probably different for other writers, but where I feel most vulnerable, most at stake, and most exposed in writing is in fiction. A step I took recently just brought home how true this is for me.
Poetry is almost all artifice. It is so highly stylized and smoothly polished that the personal element is nearly thoroughly disguised. What the reader is exposed to is sheet artifice, verbal fireworks, or highly compressed verbal energy. The poem may explode, it may inflate, it may do any number of things--it may reveal personal moments, but they have been sharply curtailed by the point and purpose. My poetry exposes me to almost no risk. Does anyone really think that Alan Ginsburg is one tenth as interesting and lively as his poem "Howl" would have one think? And what of Keats and Blake? Even Sylvia Plath, whose poetry was intensely personal manages to set the personal at a great ironic distance most of the time (read "Lady Lazarus" or "Daddy." The poet is not on display there--the language is.)
Non-fiction poses few hazards because you pick and choose what you write about in such a way that you reveal what you care to reveal, which means, in essence, you reveal nothing at all. The intimate memoirs, the auto-biographies, the telling personal exposes--all tell you exactly what the authors would have you know about themselves.
Fiction, on the other hand, is dangerous. You pick and choose your stories. You write your story lines. But there is always the danger that the story will get away from you--that you will stand exposed because you have pressed yourself out of it the way you do in a poem. Fiction is a case of "give 'em enough rope." Nearly every author stands exposed in his or her fiction. The interesting fact is that they do not stand exposed in the way most people think they do. The narrator or events is almost never the author. But there are undercurrents, little things that even in the fourth, fifth, and sixth drafts of a work the author doesn't notice--but these tell-tale signs are there for any astute reader to observe and decipher. Or so it seems. The likelihood that anyone will intrude upon the correct understanding of a personal symbology is infinitesimal. But because fiction is the telling of tales, and the details of the tale almost dictate themselves, and because there is refinement, but not refinement of the type that goes into poetry, and because there is selection of detail, but not of the same type that goes into nonfiction prose, each chose lays bare something of the author who penned the work.
Or so it seems to me. But then, that may be the result of the fact that fiction has led me far closer to the truth than either nonfiction or poetry have ever done. Poetry has brought me into the halls of beauty and nonfiction into the realm of sheer skepticism; but fiction gets in under the radar and I find myself "surprised by joy" and awakened to the reality that lies under the event. And this happens whether or not the author intended for it--I see a small glimpse of eternal Truth in every well-crafted piece of fiction. And, perhaps circularly, this may be because of the sacrifice the artist makes in laying him or herself bare in such a way. The defenses are still locked in place, but like a fence now, their outlines are observable and a fence can be scaled, pulled down, or dug under.
Whatever may be the case, my fiction is one place where I feel terribly exposed. And that, for the most part, is why none of it shows up here, nor is ever likely to. Eventually, I hope it will make it into print, securely bound behind the paper covers of an anonymous book--a entity I formed, but which now has a separate life. But all of that is about courage.