There’s nothing at all wrong with posting personal information on your blog. or with writing about things that have nothing at all to do with writing. Just read blogs by published writers, and you find most of them, especially the more experienced ones, do so on a regular basis. And there’s certainly nothing at all wrong with talking about the writing process. In fact, this is one of the main things writers, ranging from new and unpublished to old and widely published, writers do. Thank God.
But talking about the writing process should never mean talking about rejections (Until after a piece is sold), posting samples, etc. It simply means talking about how you write, how-to books you’ve found useful, even rate of progress. But that’s about it.
But unless you have a LOT of clout in publishing, meaning no one is going to reject your book even if you run down the street naked, all the while screaming how horrible this editor or that publisher is, it’s a bad, bad idea to use your blog as a place to complain about publishers, editors, agents, rejections, etc.
Nor should you use your blog to post unpublished work, even if you never intend to sell it. I don’t even like excerpts of unpublished work? Why? Simple. St may not be very good writing, and bad writing on your website or blog can scare away agents and editors. The last thing you want on your website or blog is writing that simply isn’t good enough to impress agents and editors. Save excerpts and entire stories until after you’ve been published. At this point, an excerpt can spur sales, and an out of print short story can attract readers.