Writer Shirley Hazzard said: "The state you need to write in is the state that others are paying large sums of money to get rid of."
This is true. You'll need to make friends with your anxious, twitchy, vulnerable self in order to write regularly. Note: this "creative anxiety" never disappears. You do however get used to it. Over the years, I've come to understand that without this uncomfortable tension, creativity is impossible. So if you feel anxious just before you write, realize that it's just a mind state, and will evaporate as you work, and that you NEED to be in this state in order to write.
Note: it takes around ten minutes to change a mind state. See my article on "Training your creative self".
In addition to awkward emotions, you may also feel that your writing efforts aren't good enough. This is because you're surrounded by words every day, in print and other media. It's intimidating. Remember that these words are polished, professional words. Work and effort has gone into those words, but the effort doesn't show. The first drafts of a professional writer's words are just as crappy as your first drafts, but the professional doesn't care. He knows that just getting ANY words written is a victory.