Productivity is hard! I am also struggling to find new ways to be more productive and am trying a few new things this week:

Remove HN from bookmarks. My only news comes from feedreaders, and HN is for finding new blogs only.

Work in text mode. Keep all distractions as far away as possible. For writing the equivalent would be pen & paper instead of using the computer.

Pomodoro. Feeling rushed can help sometimes. Anything that gets the adrenaline pumping seems to help.

Good suggestions. I haven't tried Pomodoros yet, but it's been recommended by smart people so I will eventually.

This particular instance went beyond just "not procrastinating" - everything was clicking, making sense. I'm back awake at 6:30AM here and working, with a coffee and some bread with peanut butter, and I'm just not there in the same place. Bah. It was clicking, y'know?

I wish I could do that at will. With practice, maybe. It's worth working towards, anyways...

The advantage of the Pomodoros technique (and its variations) is that it gives a sense of urgency, of measured time. If that's what you need to be productive, it's really useful.

When I for example need to read a long text I sometimes estimate how long I'd need to read it (that estimation can be refined over time) and then set a clock where I can see the big numbers decreasing steadily. So when I'm behind I curse inwardly and focus more on the text and such... and if I finish early, there is this feeling of reward or accomplishment - finishing the reading of a text a minute before I would have had to suddenly seems like a big and great thing. The minute gets added to my break.

I can relate, I've had days/evenings where everything just seemed...clear. Everything made sense, but you know that eventually that part of your mind will relinquish control. You'll fall back down into something else. For me I'll have up days like that and then I'll also suffer from the opposite. The days where nothing makes sense, I hate myself, have suicidal idealization and other opposite mental attributes. I do think however that a lot of these states feed off of themselves, if you watch your mind for a while you'll notice repeating patterns of thought and emotion. You can learn to predict some of the states, and based off of that you can gain some control. I've managed to sometimes predict the down states and prepare myself for them. That way they don't become that bad. You notice when your thinking strays a certain way and you can redirect it. Or you learn that you don't actual believe any of the negative things you find yourself thinking. Instead its a consequence of hunger, thirst or some other lack in your existence. For me hunger will often represent itself as very negative emotions. I won't feel hungry, I'll just have a really negative mood.
I've been reading the Pragmatic Programmer's Pragmatic Thinking and Learning and I've found two useful techniques so far that help with this. Whenever I wake up in the morning I write 3 pages long hand first thing. I've found that this helps with getting out all of the unconscious thoughts that you've been mulling over. The second the acronym SMART for goals, Specific, Measurable, Achievable, Relevant, Time boxed. Similar to the Pomodoro technique that Jackson and SZ mention, you have to take the broad view of your goal and boil it down to specific action that you can take right now. Like Jackson and SZ I've found that this really helps for getting things done. I'm glossing over a lot of information, but that's the gist. I don't know if any of the above will help you, but maybe it'll trigger a good idea in your brain that we can all learn from.

I too find myself awake through the early morning on occasion, where my thoughts are rapid and clear, and my work is efficient, inspired. I often wonder why I do this, especially the next day after I stay awake beyond a reasonable time to hold on to the vestiges of this inspirational flow. It usually causes my next day to be slow due to lack of sleep.
For myself, I think that it may be the tranquility of the early morning which inspires my actions. I like to accomplish things when no one else is around, sometimes it makes me feel like I am doing even more because I am the only one awake, and I know I am not missing out on anything (so it seems). Possibly akin to "staying late at the office", knowing that you're doing a little bit more and therefore better off?
When I try to effect this mood and can't seem to settle into it naturally, I turn off all of my electronics. Phone, computer, music, and clear my physical space- sometimes I will clean my house for an hour until all distractions are removed, and I'll write a list of all of the tiny/inconsequential things captured that could interrupt my flow. Other times I go to my favorite book store, or library. Its not quite the same as the natural inspiration, but it approximates it due to the solitude and clarity I can sometimes create for myself. Other times I simply end up with a clean house and a stack of new books. However, I can't claim either of those byproducts to be a negative consequence. I know you keep some pretty solid lists already, so perhaps that part wouldn't be so helpful to you.
It was interesting to read your post, and good to know that I am not the only one who keeps strange hours occasionally.