If your sent story is rejected, you won't have any other irons in the fire. If it is accepted, you won't have anything fresh to offer to keep up the momentum. Not writing will make your brain stodgy. You need to keep it working.
Waiting for news is way more exciting when there are twenty or thirty stories/poems out there. Remember it can take months for a reply, so, even when you have sent out lots of work, there will be weeks when you have no news at all.
So maximise your chances and make the wait fun by sending something as often as you possibly can.