There are hard limits to what your brain can manage in a day. Ignore them at your peril.

Simon Sinek has spoken about how much value he's gotten from studying the work of his long-time professional rival Adam Grant. Watching another person do very similar work but with his own unique strengths on display, Sinek claims, both frustrated him and helped him grow. For me the person who very often makes me feel that way is Oliver Burkeman.

A former Guardian columnist and author of several books, Burkeman is not only obviously more accomplished than me, he also covers similar topics around psychology, success, and productivity. That means very often I read something he's written and realize we've seen the same studies or referenced the same author. Burkeman just frequently manages to boil that wisdom down in a more compelling and cohesive way than I do.

The most recent example is the latest edition of his excellent newsletter, The Imperfectionist, that offers an incredibly powerful approach to time management.

Four a day is all you get.

In it, Burkeman writes about one of the few hard-and-fast rules of time management he's discovered. "You almost certainly can't consistently do the kind of work that demands serious mental focus for more than about three or four hours a day," he declares. "It's positively spooky how frequently this three-to-four hour range crops up in accounts of the habits of the famously creative."

He goes on to list a distinguished list of thinkers, from Charles Darwin to Ingmar Bergman, who put in around this many hours of work a day. This might sound like a shockingly short work day, but it was no surprise to me. I have also previously covered the huge range of evidence from science, the biographies of geniuses, and even anthropology that pretty much proves our brains only have around four hours a day of work a day in them.

Sure, you can work your way through mindless admin or assembly line manual labor for far longer, but when it comes to concentrated intellectual effort, humans face a hard biological limit. White collar professionals generally reach it way before the workday ends.

Protect your core four.

So far, so familiar (to me at least), but as usual, the best part about Burkeman's writing isn't the information he uncovers, but the conclusions he draws from it.

"The real lesson," Burkeman writes, "is that it pays to use whatever freedom you do have over your schedule not to 'maximize your time' or 'optimize your day', in some vague way, but specifically to ringfence three or four hours of undisturbed focus (ideally when your energy levels are highest)."

You're going to get the vast majority of your important work done in the four most productive hours of your day no matter what you do. That's just how human brains work. Even Jeff Bezos only expects to manage three high-quality decisions each day.

So build your time management decisions around this 'Rule of 4.' Don't try to extend your core working time; you can't. And don't try to stretch it over eight (or more) distracted hours; that won't work either. Instead, pick you four golden four hours and protect them like a mama grizzly bear.

Focusing on your four core hours should help you get more done with less aggravation. It should also help you stop beating yourself up when your brain just won't produce any meaningful insights at four p.m. even though there are dozens more items on your to-do list. Laying down your intellectual labors and puttering through whatever more mindless work you can manage isn't a failure. It's a wise recognition of the basic need for rest and recuperation built into our brains. Working with those limits isn't lazy, it's the basis of sensible time management.

Inc