I've noticed that everything that's been stated involves doing something or trying something or focusing on something.
I propose elimination. See how much you can cut away from your life. Via negativa.
Eliminate needless clutter from your desk.
Eliminate needless noisemakers from your social media. (Eliminate needless social media channels altogether.)
Eliminate needless apps from your phone.
Eliminate needless blogs from your RSS feed.
Eliminate needless books from your shelves.
I think of this as an 'Odyssean' activity.
Odysseus guarded himself against temptation by the Sirens by getting his men to tie him to the mast of his ship.
Our willpower is limited.
In moments of clarity (or boredom, when we have enough energy to do simple tasks but not major ones), it helps if we tie ourselves to our masts by eliminating distractions.
Cut away anything that isn't relevant to what you want to achieve in life. Do it now, while you can, and you'll thank yourself for it later when you'd have been otherwise distracted.
Of course, you never want to get too extreme with this, because there is always value outside of what you've set up for yourself. That random annoying person on Facebook might just be the spouse of your dreams. It's pretty unlikely, though.
Trust your own judgement and get rid of what you know, with reasonable certainty, to be a waste of your time.
That leaves you with only what matters. Now that's productive.