I fired my muse. When she wouldn't stay fired, I packed her up into a box, forgot the airholes, and shipped her off to parts unknown. I'm much happier now. I can actually get things done. And my internal editor is quite quiet, too. She knows I'll do the same thing to her if she starts giving me any lip.
Yes, I know it's personification. But damnit, it helped. So all the literalists can go join my muse.
Seriously. By shipping off my muse, I took control. Slowly. But now I can stay focused on one thing at one time, and just pat the plot bunnies on the head, put them outside my garden, and tell them to run, eat, and if they survive until I'm done with my current project, I'll bring them in and feed them until they're ready to become full sized jackalope ideas. But until then, outside with them.
Outlining helps some people. Other people need to know the beginning and end, and they're off and running. To me, it sounds like your ideas are bright, shiny, and incomplete. That's often what stalls me out, the incompleteness of those new ideas. Too many plot bunnies show up with only pieces parts of a plot, amazing characters, and no point to write them. I've had stories with a very cool set-up, but getting them to do anything was like pulling teeth. So I sit and stare at the problems, knowing that they're just going to plague me until they either start coming together in a cohesive manner or fall apart into an icky messy diaster.
For me, it's critical to make sure everything hangs together in a story--plot, character, theme, worldbuilding, sparkle, and all those other things that make up a Story. If something doesn't hang together, it'll stall me out until I figure it out. I don't like that feeling, so I outline outline outline before I write so I avoid that out of control feeling, which avoids delays and such.
You'll have to figure out your own method for putting butt in seat, fingers on keyboard or wrapped around pen with paper, and writing.
p.s. sorry if this is somewhat incoherent. Sleeping pills do that.