Something that's helped is that I've been reading inspirational essays about the creative process before I write. NaNoWriMo pep talks, Anne Lamott books, quotes on Pinterest...anything to put me in a positive frame of mind. I've found that it's hard to hold a positive thought ('Creativity is necessary for my well-being') and a negative thought ('Editors are going to hate my work, I'm a fraud') at the same time.
Other things I've done have been storytelling games like Dungeons & Dragons, story analyses, free-writing, and writing the silliest story I could think of (a ghost gets a physical and realizes that she's turning into a human again, which is very distressing because she has tea scheduled with her friends next week). For now, writing means focusing on the fun and the interesting parts and doing everything I can to disengage my idea of writing from the idea of publishing, even to the point of not writing down my word counts or making story decisions with a 20-sided dice.
TI made myself write until I'd done three chapters, left it a few days, then read them over. The words came so hard that I was expecting terrible things, but I actually really enjoyed the chapters (still found plenty to red-pen, but that's fine). I gave them another polish and felt they were good enough to send to my agent.
And today I wrote a SYNOPSIS without vomiting blood! WIN.
One thing I've realised through this block is that I'm very motivated by feedback. If I can squeeze out a few paragraphs and get instant feedback from my CPs, good or bad, I find it much easier to carry on. Ultimately what I want isn't fame or fortune but for people to read my books and feel something, and for that to happen I need to write the damn things. Focusing on that goal has been helpful, too.
(P.S. Cthulhu, if you're listening, I will totally accept fame and fortune as well. Thanks.)
In wargames, we call your condition "Analysis Paralysis".
I get you perfectly. I refused to write for a long time because I was terrified I couldn't live up to my favorite authors. When I finally started, I finally realized that I lived up to me. I like what I write. If I like what I write and I like what authors that I favor write, I could be doing ok. LOL
And you are, too.