I block 8:30 to 11:30 for deep work. It’s a three-hour hold. I expect 60 to 90 minutes of focused work, a 15 to 30 minute walk or reset, and a second cycle after that.
Your circadian rhythm is the 24-hour sleep-wake cycle. Ultradian rhythms are the shorter cycles inside it, about 90 minutes of alertness rising and then falling. Writing on full engagement describes the same cycle. After about 90 minutes of intense focus, cognitive performance naturally declines. I build the day around peaks, valleys, and recovery. Five straight hours of focus ignores that shape. Work in 30 to 90 minute chunks, with a real break between them.
I compare it to protein. A daily goal of 160 grams still has a sweet spot, and 100 grams in one sitting overloads it. Overload creates diminishing returns. I spread focus across cycles I can repeat, the way you’d spread protein across meals.
Take Brooks’s rule. Aim for 90 minutes. When you get 15, 30, or 60, use the window you have and improve it one tweak at a time. A 15-minute window counts. So does 30. So does 60. Ninety minutes is a target. Treat it like one.
Train with Pomodoro, then stretch it
Pomodoro can be training wheels for focus. Twenty-five minutes of work, five minutes off. If that’s all you can sustain, use it.
Brooks raised this, and I agree. Strict Pomodoro can leave capacity unused. Pomodoro is useful conditioning. Once the focus muscle gets stronger, experiment with a longer block. Go 25 minutes, then 45, then 60, then 90. Next time, chain two cycles before you break. That’s about 50 minutes of work. For deep work, 25 minutes is often too short to reach flow. Keep the short timer for low-energy tasks, or for a day when 25 minutes is all you can sustain.
Timer goes off and you still feel sharp? Stay with it.
Find the hour that can hold the work
Brooks puts self-awareness at the center of this. Chronotypes differ. Some people dive into deep work the moment they wake up. Others need a 30-minute warm-up. The 90-minute rule is a starting point. Match the type of work to the quality of energy you have in that hour.
Track your energy for a week. Short on time? Do a 3-day audit and rate your focus every hour. Mark the peaks. Mark the valleys. Put your most important outcomes on the peaks, and schedule lower-cognitive tasks in the valleys.
Which hour did you rate highest? That’s where tomorrow’s real outcome goes.
Leave the workstation
Brooks keeps work and breaks in different places. When he takes a break, he leaves the computer. He says he does this 100% of the time. Another room for water or a snack. A different room. A physical book for 15 minutes. That shift in environment and mindset lets the brain reset for the next cycle.
A true break means you physically leave the workstation. Staying at your desk to check social media or email is a context switch. It blocks cognitive recovery. Recovery is part of the work.
Pick the non-screen break before you start. Water, a snack, a short read, another room. One of those, done on purpose.
Surf a messy day
For parents and caregivers, the workable version is surfing. Brooks captured whatever window appeared. Five minutes for a sentence. Fifteen minutes for editing. An hour when an hour showed up.
A familiar writing practice fits this life. Five minutes, write one sentence. Fifteen minutes, edit a paragraph. An hour, write a page. The day stays interrupted. Each window still gets a piece of the work.
Look at today and find one micro-window. Give it the sentence, the paragraph, or the page that fits the minutes.
Book Monday before the meetings do
When the calendar is packed, deep work may need an early hold. Reserve the focus block before the week locks up, because meetings take open hours if the hold waits.
If the work matters, protect the block early. Treat a meeting request as a trade-off against the outcome already in that hour. Book the focus time before other people claim it.
Ask what moved
The question I want at the end of a day is, what outcome moved forward? Twenty small tasks can get checked off while the one result that mattered sits still. Picture a college student who finishes 20 tasks, with only one aligned to the goal. Counting finished tasks is easy to game, and it misses the impact.
An outcome is a clear objective, like implementing a system that saves 3 hours a week, and it may need several tasks inside one focus block. The tasks are the activity. The outcome is the destination. Write the outcome on the block before you list the tasks. For the week, name your top 3 outcomes.
The same trap shows up in AI metrics. Companies measure adoption by tokens burned or by the number of prompts. It works like measuring police effectiveness by tickets written. People generate useless content to hit a quota. Review your team’s AI metrics. Are they measuring activity or impact? Score the value created.
Tonight
Open tomorrow’s calendar. Rewrite your top task as a single outcome, and place it on the window you can honestly hold. If you have 15, use 15. If you have 60 or 90, take it. When the window ends, stand up and leave the screen. Ninety minutes is the target.
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