Some days I feel fucking great. Like I can take on the world. Do anything. I'm motivated, want to get things done, and feel like I can do it. There's not a hint of fog in my brain, not a bit of fatigue in my muscles. It's awesome. I leap out of bed, think "damn, I feel great!" and just go.

But... it's also only 5-10 days a year, and seems to hit more-or-less at random (though sunny, long, not-too-humid days seem to make it a lot more likely).

I imagine the people who seem to have an easy time doing lots and lots of productive stuff have a lot more days like this per year than I do. So figure out how to feel that way, say, 50-100 days a year and you're on the right track, I'd say (for a shortcut, see the other post about drugs). Unfortunately, I'd guess there's a strong genetic component to it.