One thing that always would hold me back on writing a screenplay would be always going back and checking and double checking I wouldn't really get anywhere with my screenplays and really the best thing to do about that is just write from the heart don't pay too much attention thats why its a first draft just hammer out really the basic blue print of your script and then go back and do re-writes and add things in the ultimate cure for writers block is just simply not criticizing yourself so much