If showing up is 98 percent of success, then just starting to write has to be a solid way to get over writer's block. Write anything. Write everything. Just as long as you're writing.
And that's what I've been doing, and I'm kicking my book proposal into shape and it's actually starting to look like the book proposal of someone who knows what they are doing. If I can just convince part of my brain that I actually can successfully write a book proposal--an ultimately a book--then that has got be the hardest part of getting through this rough patch. And even if the rest of my brain is skeptical, I just need part of me to believe in me. I'm certain that my own fear of failure has to be the most significant part of my writer's block. But I refuse to be defeated. I've armed myself with some how-to books and I'm writing and writing and writing. Some of it is garbage (and that is all part of the process), but at least I'm making progress in the right direction.
I think one of the things that helped me was that I did an image search on Google for "published author." My blog is in the process of being redesigned and I wanted to get some ideas for how to visually say writer/author without using an old typewriter, like I did when I ordered my official business cards a couple of years ago. And the search results showed a lot of people who look less capable than I do of writing a book. And so I thought, if all of these people have published books, then I most certainly am capable of publishing a book too.