The worst thing you can do as a writer is to endeavour to write a “great” script as achieving greatness is a daunting thought, and for some paralyzing. Try instead to make each draft BETTER. Your next draft doesn’t have to be great, just better. Identify an area you need to work on, for example a character, or the dialogue, and make this aspect better. Then move on to another aspect and make that better… and better… And gradually, piece by piece, the whole script improves. It’s a less daunting way to greatness. On that note, here’s an article I read which might help writers out there who feel crippled by perfectionism.