That's what it's for
The vulnerability in writing is different from that of letting people into your real life. It's more like peer review in the sciences -- that is, I've always held that it should be. On the other hand, by virtue of The Hiss I've become one of those peers de facto, with no more qualification than the Scarecrow had before the Wizard named him Doctor of Thinkology.
Vulnerability to a writer is: rejection slips. We want, most emphatically, to be read. Why else do it?
Besides, despite the tendency for readers to assume autobiography in others' words (especially poems, I've found), there's no telling which passage is drawn from life and which from a lifelike imagination... is there?