A post from my Personal Journal (which is a private blog). It seems relevant here too.
I re-read some posts here [Personal Journal] which, at the time of writing, felt private, and I realise there is no need to keep them secret. I shift them to my Widowhood Chronicles.
It's good to write them at first as private, though — I'm more inclined to let it all hang out when I do that, and I note that this makes for better writing.
They could, of course, stay private. It's up to me.