You should quit trying only after two conditions have been met: 1.) You've given yourself a legitimate shot. 2.) Trying is no longer fun.
Terry RossioMost aspiring screenwriters simply don't spend enough time choosing their concept. It's by far the most common mistake I see in spec scripts. The writer has lost the race right from the gate. Months - sometimes years - are lost trying to elevate a film idea that by its nature probably had no hope of ever becoming a movie.
Terry RossioYou are an adult when, faced with important decisions, you choose to have more faith in yourself than anything else.
Terry RossioI'm tempted to say, 'Writing treatments is like designing a film by hiring six million monkeys to tear out pages of an encyclopedia, then you put the pages through a paper-shredder, randomly grab whatever intact lines are left, sing them in Italian to a Spanish deaf-mute, and then make story decisions with the guy via conference call.' But no... compared to writing treatments, that makes sense, too.
Terry Rossio