"I have been successful probably because I have always realized that I knew nothing about writing and have merely tried to tell an interesting story entertainingly."
Thick skin, and a desire to produce a great movie will get you through a lot. Screenwriting is re-writing. Others will tell you (over and over) to change what you’ve deemed perfect. Get used to it. Don’t be cocky or defensive about it.
Simply understand that everyone (even the idiot making ridiculous suggestions to your perfect story) wants to make money from your screenplay. Humility and a “can do” attitude will make life much easier for all involved.