In the book, "The Secret Miracle," Shelley Jackson (""Half Life") says, "I sat on an unfinished first draft for years because I suspected, correctly, that I didn't know how to finish it. When I finally went back to it, I still didn't know how, but I went ahead and did it anyway."
She adds, "I wish someone had told me in the beginning I would never know how to write a novel, only how to carry on despite near-total confusion and doubt, and how, once I finished a draft, to figure out what I'd done and make it better."
If you're stuck because the only next step you can think of doesn't feel like it's the right thing to do, and brainstorming doesn't bring up any better alternatives, do the "wrong" one. In the process, you may find that you start to understand better what would be better.
Sometimes when you're lost, the best thing is to start in one direction and pay attention to the clues. Going the wrong way may help you find the right one.
(There are loads of practical tips for generating ideas and keeping your motivation high in my book, "Your Writing Coach," available from Amazon and other online and offline booksellers.)