Sometimes you have writers block, it happen even if you need to write an e-mail, a blog post or some software, not just if you are writing books, you are sitting on your chair, your hands are on the keyboard but nothing comes out, one way to get past that is to find a simpler easier version of what you have to do and do that first, for example:
Writing a good long blog post about technical subject that requires research is difficult, writing a short rant about some minor computing annoyance is easy.
Designing a new web site is difficult, tweaking...