First off, I have nothing to say that you don’t already know. But let me ignore that point. The way to become a better writer is to write. The way to become a more comfortable blogger is to write blog postings. It’s as simple (or as hard) as that. You don’t need to agonize over it. Just do it.
Okay, so let me respond to your specific points: I think you’re working from some faulty premises. On the one hand you suggest that a blog posting has to be a magnum opus. “[S]truggling for breath on a mountain trail and then suddenly finding myself at the top. ” Great metaphor and I agree that sometimes writing can be like that, but blogging? For me, rarely. Later you say that blogging should be spontaneous. I don’t think blogging can be both.
I wonder if you’re trying too hard or maybe thinking too hard. Blogging should be like breathing –something you just do without too much conscious effort. Sure, you want to express your point correctly and well. So just do the best you can and let it go. Blog postings aren’t intended to be finished publications. You think your ideas may be half cooked? Why don’t you let your readers decide? I’ve never thought that about any of your posts. The worst reaction I’ve ever had is, “This doesn’t really interest me,” but even that, rarely.
Personally, I don’t worry too much about getting posts published. I tend to write them in three steps: First, when I first get an idea for a posting, I open a new post and jot my notes down. Next, I come back, usually at least 24 hours later, and write a first draft of the post. This is for me the hardest step, and I often do it in several sessions. Finally, I come back a third time and polish the post. I almost never write an post in one try. In fact, at this moment I have 9 posts in various stages of construction, some going back months. It is true that sometimes a partially finished posting gets dated and I delete it. But I don’t worry about that. There’s always something else to write about. Something that someone might find interesting.