On progress When progress is stifled, you have to zoom out and figure out how the entire machine works to get it running again. The small tasks are simple. Wheels move on the axle. This gear turns that gear. All of those small functions may be fine, but the entire machine still isn't moving. You'll find that the problems that really impede progress are much larger than those granular issues. Perhaps the machine does move, but it goes in the wrong direction because you are not steering properly. Maybe the driver doesn't have a map and is driving the vehicle aimlessly. Don't get trapped in technical lock and forget about the big picture. A mechanic will tell me that the reason my car isn't making any progress is because of a mechanical issue. That is what he knows. If that's what's wrong with it, he can fix the problem. However, that may not be the problem. You have to be the one, as a leader, to zoom out, decide what the real problem is, and fix it to make progress.
On multiple projects I'm not sure if having multiple projects is conducive to your success because it seems to paralyze you. With so many pieces of writing you want to get done, your mind doesn't focus on any one of those and they are slow to move to completion. I've even observed you procrastinate the writing by staring at the page and trying to figure out what you're talking about in the first place. For now, until you prove to be more adept at writing, focus on one project at a time. Pride yourself on leaving few things unfinished. You have to learn to go through the entire process of writing—drafting, revising, editing, polishing—before you can begin to split those parts up with ease. Once you are proficient in all four of these, then you can take on multiple projects at multiple stages and always understand how to pick those projects up mid-stream and take them to completion.
On thinking You're wasting your time trying to power through tiredness. However, you're not wasting your time breaking through a lack of ideas. If you've hit a dead end and want to put your current project down for a few minutes, stay there. Stay in front of the page writing for a longer period of time than you usually would. Dump the rest of the contents of your brain out, even if you're only repeating things you just wrote. The goal in the early stages is not to produce a final piece but to find insights. Writing and speaking have to be synonymous with thinking. Use the moments before you put down a project to specifically exercise this skill and see if you can squeeze out any final ideas on to the page. (And don't get discouraged when they don't show up.)