Well, I did what I said I was going to do yesterday -- got over the post-submission fretting and worked on a new story. In fact I started something new, rather than working on a WIP. I was poking around the Dreamspinner Press site, where some people I know have sold recently, and saw that they have some open anthologies accepting submissions. I got an idea for their Mr. Right Now anthology (submissions due by 30 November) about an encounter on the trail while on a hiking/camping trip and dinked around with it a bit and got a few hundred words down.
Which is all great except that while doing something else I got another story idea which would fit their Know When to Hold 'Em anthology. [laugh/headdesk] I'd originally passed that one over because both the title and the cover art imply the old West. I don't know enough about cowboys and such to do a decent job with that sort of story without a lot of research, and the deadline is 30 September. But the description says they'll take "tales of cowboys and gamblers from around the world and throughout time" and I got an idea for a gambling-themed story. It's also a fantasy but that just means it's less likely to be exactly like thirty other stories they get, right?
Anyway, usually I'd jot down the basics of the new idea and keep working on the old one, except that the new one has a deadline a month before the old one. So it looks like the hiking story is going to be shelved for a bit, at least while I poke around with this new idea and see if it pans out.
Dreamspinner has several open anthologies, though -- check out their Current Calls for Submissions page.