Verrrrry good idea to work on one script… get a draft done… put it away and start another script. It will take a long time to get the second script’s first draft done.
While you’re solving the problems of script #2, you will mostly forget what you wrote in script #1. From time to time, you may make a note of something to do on #1, but concentrate on #2.
This is a superb discipline.
It keeps you from thinking, “Hey, my screenplay is finished. It’s ready to send out!” because you are busy working on script #2. If you’ve only got the one script, you’re going to invest all your energy in it, and wanting to collect your richly deserved Academy Award. No one would want an Academy Award TOMORROW, if they thought they could get it today… right? But if you’ve only got the one script, chances are that you’re going to send it out before it’s as perfect as possible… and you will have wasted your time and that of the kind and gentle soul who agreed to read it.
Or the complete asshole who agreed to read it. Who knows.
If you move from script #1 to #2, when you have at last have a draft done of #2, come back to #1 and the flaws will have exposed themselves to you, like a flower opening up.
Go back and forth until you finish #1, and then start #3, so you can bounce from it to #2.
Pretty soon, you’ll have a body of work. But don’t just write one at a time. It’s a recipe for doom. And we don’t want that.