Hello my friends,

You make roughly 35,000 decisions a day.

What to wear. What to eat. Which email to answer first. Whether to speak up in a meeting or hold back. Whether to take the call or let it ring. What to say, how to say it, when to say it.

Most of these decisions are so small you don't even register them. But your brain does.

Every single one takes a small withdrawal from the same mental bank account. And by the time you get home in the evening, that account is running dangerously low.

This is why your day looks like this:

Breakfast — healthy. Lunch — pretty good. Afternoon — still holding strong.

Then 8pm hits.

You order takeout instead of cooking. You scroll your phone instead of going for a walk. You stay up watching one more episode instead of going to bed.

I lived this pattern during my second trimester.

I was working full-time as a physical therapist, studying everything I could about newborn care, and trying to keep my health habits intact. I had prepped meals in the fridge. Good ones. Plant-based, ready to go.

But by the time I got home, I was so mentally spent that even microwaving a prepped meal felt like too much.

So I ordered takeout. Repeatedly.

The meals were still mostly plant-based, but I had no control over the sugar, salt, or fat that restaurants add. Cooking would have been healthier. I knew that. I just couldn't make myself do it.

And for a long time, I thought that was a discipline problem — like I just needed to try harder at the end of the day.

I was wrong.

It was never about discipline.

It was about my brain being chemically depleted.

In 2022, researchers published a study in Current Biology that changed how I think about willpower.

Wiehler and colleagues had participants perform cognitively demanding tasks over the course of a full workday while scanning their brains.

What they found was striking: a chemical called glutamate accumulated in the lateral prefrontal cortex — the region of your brain responsible for decision-making and self-control.

As glutamate built up, participants started choosing easier, lower-effort options that offered quicker rewards.

They weren't being lazy.

Their brains were physiologically fatigued.

Think of it like this: if you did bicep curls for six hours straight, you wouldn't blame yourself for not being able to lift a grocery bag that evening. Metabolic byproducts build up in the muscle. It loses force.

The same thing is happening in your prefrontal cortex after a day of cognitive work. Glutamate builds up. Your capacity for effortful choices — like choosing to cook instead of ordering pizza, or going for a walk instead of collapsing on the couch — degrades.

Not because you're weak. Because you're spent.

This is why the pattern is so predictable.

You don't fall apart at 8am. You fall apart at 8pm. You don't struggle with decisions when your tank is full. You struggle when it's empty.

And if your job involves making decisions all day — managing people, solving problems, answering questions, evaluating options — you are draining that tank faster than most.

So if the problem is too many decisions draining your brain, the fix is straightforward: make fewer of them.

Not fewer important decisions. But fewer repeated decisions.

Think about how many health choices you're making fresh every single day.

What should I eat for breakfast? Should I work out today? When should I go to bed? What should I pack for lunch?

Each of these costs mental energy. And you're paying that cost over and over, day after day, for the same choices.

The principle I use is simple: Decide Once.

Instead of deciding what to eat for breakfast every morning, make that decision one time and let it repeat. One decision now eliminates hundreds of future decisions.

You pay the mental cost once, then it runs on autopilot.

I've eaten the same oatmeal breakfast on weekdays for about three years now.

I started doing this while studying for my Lifestyle Medicine board exam — I was deep in coursework, working full-time, and I didn't have the bandwidth to think about breakfast every morning on top of everything else.

So I decided once. Oatmeal. Every weekday.

Before that? Right after college and in grad school, I mostly ate junk food or skipped meals entirely. I didn't have a default — so I defaulted to whatever was fastest, or nothing at all.

And that's the thing people miss: if you don't choose your default intentionally, you're still defaulting. You're just letting a depleted brain choose for you.

That's not freedom. That's being controlled by your circumstances.

"But doesn't that get boring?"

Honestly? It did at first.

So I started tweaking the toppings every couple of weeks. Different fruits, different nut butters, seeds, spices.

One summer I switched to fruit smoothies for a few weeks, then went back to oatmeal when the weather cooled down.

That's the flexibility within the structure.

The decision — what I eat for breakfast on workdays — is made. The details can shift. You can let a "Decide Once" choice last for weeks, months, or years. And if you notice it's not working anymore, you iterate. You try a different default for a while.

You're not locked in forever. You're just not spending mental energy on the same choice every single morning.

Your version doesn't have to be oatmeal. It could be a smoothie, a grain bowl, the same packed lunch three days a week. The specific food doesn't matter. The decision being made in advance is what matters.

This principle works anywhere you're making the same health decision repeatedly.

And here's one that might surprise you: I subscribe to a fitness app so I don't have to think about what exercises to do during my workouts.

I'm a physical therapist and a certified personal trainer. Designing exercises — even making them up on the fly — is literally what I do for my patients every day.

But I learned that if I added designing my own workout plan to my list of daily decisions, I'd just end up not exercising at all. The mental cost of one more thing to figure out was enough to shut the whole thing down.

So I decided once: let someone else program my workouts.

Four years ago, I attended Muay Thai kickboxing classes at an MMA gym. When my work schedule got busier, I switched to home kickboxing using the FightCamp app.

Last year, during pregnancy, I used the Ladder app for my prenatal exercises.

The format changed with my season, but the principle stayed the same — I removed the decision of what to do so the only decision left was to show up.

If a physical therapist and personal trainer needs to outsource her own workout programming to stay consistent, you probably do too. And that's not a weakness. That's strategy.

Look at your own daily health choices.

Where are you spending mental energy on the same decision again and again? That's your candidate.

When do you go to bed on work nights? Decide once.

When do you exercise? Decide once.

What do you eat on your busiest days? Decide once.

Each one of these frees up a small piece of your cognitive budget. And those small pieces compound.

By evening, you have a little more left in the tank — not because you built more willpower, but because you spent less of it on decisions that didn't need to be made fresh.

One distinction that helps: your work days and your off days don't need to look the same.

On work days, your brain is under heavy cognitive load. Those are the days for strategic autopilot — lean on your defaults, keep decisions minimal, protect your mental energy for the work that actually needs it.

On your off days — weekends, or whatever your schedule looks like — you have more time and more mental capacity.

That's when my husband and I experiment with new recipes, try a different restaurant, or explore something outside our usual routine.

Flexibility lives here.

This isn't rigidity. It's being strategic about when you spend your decision-making energy.

Autopilot on the days your brain is being taxed.

Freedom on the days it's not.

You're not falling apart at 8pm because you lack discipline. Your brain is doing exactly what a fatigued brain does — it defaults to whatever is easiest.

The glutamate study confirms what you've probably suspected: by evening, the tank is low.

You can't refill the tank by trying harder. But you can spend less of it during the day.

So I'll leave you with this question:

What's one health decision you're making every single day that drains you — not because it's hard, but because you have to decide it every time?

That's your Decide Once candidate.

Make it once. Let it run. And save your brain for the decisions that actually need you.

With gratitude,

Grazelle 🌱

PS: Speaking of the Ladder app — if you're looking for a way to Decide Once on your workouts, I genuinely recommend it. I'm not affiliated with them and they didn't sponsor this letter.

But I do have a referral link so you can use it 7 days for free:

If you subscribe through it, I get a $25 credit toward their merch. Worth trying if you want to take "what should I do today?" off your plate. 🙂

Whenever you’re ready, here are some other (free) resources you can check out: