Once you get agents or managers to read your material, find out WHY they don't want to take you on as a client. Just the script. Only the script. In proper format. Like the pros.
People are reluctant to burst someone's bubble with cold truth.
It might be hard to take, but criticism is part of the business that you'll have to get used to. A writer friend of mine has a three comment rule. He gives his draft to a bunch of writer or development friends and asks for feedback. If he hears the same note three times, he changes it. Otherwise, he defends his position or chalks it up to personal taste.