I have so many things out at magazines and contests right now, I'm afraid to send anything else out, in case I have already sent it somewhere. Of course, I haven't kept track of what I sent. So I'll let it ride for a while, and promise myself that I will note in the future what I sent out to whom and when.
It reminds me of the many job hunts I have carried out in the past. There is always the feeling that the next one or the next will do the trick. So I kept on going. But I think I have much more luck with sending out my work than with applying for jobs. I hope that holds true when it comes to farming out a manuscript, but it probably won't.