I've been writing for most of my life. The book Writing Without Teachers introduced me to one distinction and one practice that has helped my writing processes tremendously. The distinction is between the creative mind and the critical mind. While you need to employ both to get to a finished result, they cannot work in parallel no matter how much we might like to think so. Trying to criticize writing on the fly is possibly the single greatest barrier to writing that most of us encounter. If you are listening to that 5th grade English teacher correct your grammar while you are trying to capture a fleeting   thought, the thought will die. If you capture the fleeting thought and simply share it with the world in raw form, no one is likely to understand. You must learn to create first and then criticize if you want to make writing the tool for thinking that it is. The practice that can help you past your learned bad habits of trying to edit as you write is what Elbow calls "free writing." In free writing, the objective is to get words down on paper non-stop, usually for 15-20 minutes. No stopping, no going back, no criticizing. The goal is to get the words flowing. As the words begin to flow, the ideas will come from the shadows and let themselves be captured on your notepad or your screen. Now you have raw materials that you can begin to work with using the critical mind that you've persuaded to sit on the side and watch quietly. Most likely, you will believe that this will take more time than you actually have and you will end up staring blankly at the pages as the deadline draws near. Instead of staring at a blank start filling it with words no matter how bad. Halfway through your available time, stop and rework your raw writing into something closer to finished product. Move back and forth until you run out of time and the final result will most likely be far better than your current practices. What is the chief objective of the first stage of writing?
To organize one's thoughts logically. To get one's ideas down. To choose an appropriate topic. To collect raw materials.