I just finished a 10 week writer's workshop and aside from the valuable critiques and the pressure to have something written *for* critique (a good thing!), one of the best pieces of advice I learned was have the next submission ready.
As soon as something comes back not accepted, send it to the next market. No time for whining, self-pity, or second guessing. Send that puppy out.
So I'm off to the post office to send a few puppies out. (Metaphorically speaking, of course. No puppies were harmed in the making of this post.)