Improvements in my writing

What do you want to be able to do as a writer?
I have always enjoyed writing, but often get stuck on getting started. As I progress in my writing skills, I hope to be able to express myself freely. So often I think I have to have the perfect introduction for my paper to have any merit that I often block out ideas that are flowing through my head. I need to learn that brainstorming and getting ideas out on paper will help my writing process and that perhaps my main thesis or introduction will come later, after I have some concrete ideas down. I think this would greatly improve my writing and ease some of the barriers I often feel when beginning to write.