One big cause of anxiety for a lot of writers is imagining the negative response of a potential reader.  This is a particularly potent anxiety trigger for people who have been harshly criticized for their writing in the past. A single harsh comment can emotionally resonate through years, adding to the emotional stress whenever memory of it pops into mind. Whether it was some authority figure of youth or a more recent cutting remark, such thoughts can really interfere with writing: not only do they trigger or amplify anxiety, they draw attention to the wrong aspects of your work. In a previous post, I discussed the difference between writing for practice (with no audience in mind) and writing for performance (with an audience in mind), and argued that you should write for practice to help reduce anxiety.