Begin writing by hand in a notebook (preferably a Mead composition book). This lets you know that this first draft is only for you. It doesn't matter if it's "good." You are free to just write. When you finish, take a break. Get a coffee, take a walk, smoke a cigarette, listen to music, watch a movie. Then, later, type your handwritten draft onto your computer, editing as you go. When finished, read over it a few times, making small corrections. Then you're done.