Towards the end of my 20s and the beginning of my 30s, I suddenly gained the remarkable ability to see my cognitive fuel being depleted as a day goes by. At a party I’d probably describe it as, “It’s like I can see the amount of brain juice I have left for the day. Each time my brain takes a sip, I can feel it.”

Anyway. One of my goals each day is to deplete the day’s allotted brain juice before the 24 hours are up. That’s how I know I tried my best that day. Tomorrow, if I sleep eight hours, I get a full tank again.

What’s interesting about this ability is that I have started noticing how much thinking (and brain juice) goes behind making small, seemingly trivial decisions.

One of the decisions I make multiple times every single day is “what should I do now in my free time?”

The few hours after work, the one hour when my wife sleeps on the weekend and I’m completely alone, the few minutes I have between running errands on the weekend. These wonderful pockets of free time show up only when unplanned, so I’d always have to think about what to do with it.

Oh, look, I left that book on the tea table. I should read that! Hmm, but maybe I should organise my blog and create a ‘start here’ page because I find it hard to remember my favourite articles. But man, I shouldn’t! What matters more is the content of a blog, not its usability. Perhaps I should just write an article now. Plenty of ideas in the backlog. Oh wait, Simon from work recommended a new Netflix documentary about Berlin today. He sounded very enthusiastic about it. Maybe I should relax and watch that…

That inner chatter goes at 3,000 rpm and guzzles my brain juice. It’s annoying and it’s unnecessary. I could use that juicy brain to make art, read stories, learn skills, or try to achieve something.

What I have found to be effective in helpng me waste less juice is to figure out my single, preferred default activity.

When I’m alone and have free time, my preferred default activity is to write. It doesn’t have to be writing for publishing; it can be writing for reflecting and clarifying, or writing for fun.

I write on my phone if I know that I may be interrupted by someone physically near me. I write on my laptop or my Freewrite if I know I won’t be interrupted.

Since I’ve had this clear default activity, I’ve noticed that I waste almost no brain juice in deciding what to do. Got free time? Okay, I’m writing.

Over time, I believe I can further refine this to be a few defaults depending on conditions. For example, there are 30-minute blocks of free time, and there are 2-hour blocks of free time. For the shorter kind, perhaps I might edit a draft instead of writing a new one. For the longer kind, I can recognise its preciousness and go straight into doing some uninterrupted, flow state writing.

If you’ve never tried having a default activity, I recommend trying it. You will have more energy during that activity for the rest of the day.

One thing to bear in mind if you do try this: it will probably take you some trial and error to arrive at a sensible default for the unique person that you are.