Emily Lackey's post "When to Submit Again" lit a fire under me--i'd been putting this off for a few weeks now, due to double shifts in the day-job realm. So today has been about resubmission of short form work.
Every time i submit a short story or an essay to a magazine, anthology, or journal, and it comes back rejected, i do one of two things.
If it was a form rejection, i take a look at the work and see about revising it, then send it back out to some other magazine, anthology, or journal.
If it was a personalized rejection (usually something like, "while we appreciated your story concept/style/essay structure/etc., we have ultimately decided to pass, best of luck placing it"), I just pick another market and send it right back out.
I do these things religiously, or I try to. Sometimes i let it slide for a few weeks, a month, but I try never to have anything that I consider "finished" just sitting around in a folder somewhere. I want done things in the hands of people who might publish them. Sometimes it has taken me several years and countless revisions to get something placed and in print, but I rarely totally give up on something. I have taken ideas and started over from scratch. I've rewritten short stories into short play scripts. I've hacked things to a third of their original length.
What i don't do, what i never do, is let a rejection stand as the ultimate judgement on something i've written. We must, as writers, never give up on our art.