Success, in whatever way you choose to define “success,” comes down to what you do — over and over again. But every action starts with a decision. That’s why most successful people have a process for making decisions.

Oprah Winfrey decides which bridges to cross and which to burn. Jeff Bezos spends little time weighing the pros and cons of easily reversible decisions. Steve Jobs felt trusting himself made all the difference.

Good stuff, but there’s an even easier way to start making better decisions.

Just think of your brain as a muscle.

The Neurobiology of Decision Fatigue

Here’s why. To function, your brain breaks down nutrients to release energy. Byproducts of that metabolic process, like glutamate, naturally build up and don’t get cleared away until you sleep.

Unfortunately, difficult mental tasks that require focus and concentration lead to a build-up of glutamate. Too much glutamate in your system affects your lateral prefrontal cortex — the part of the brain responsible for decision making and planning — in a significant way.

How significant? A 2022 study published in Current Biology placed participants in two groups. One group did difficult tasks requiring focus and concentration for 6.5 hours. The other group spent the same 6.5 hours doing similar but much easier and simpler tasks. When tested, fatigue markers like high glutamate levels were found in the “difficult task” group, but not in the “easier task” group.

Researchers then gave participants a series of choices about whether to work harder or less hard physically and mentally, and how long they were willing to delay gratification.

You guessed it: the “difficult task” group took the easy routes, and took a lot less time to make those decisions.

Other research backs up that finding. Most people are more likely to make rational decisions about high-risk propositions earlier in the day. Most people are much more likely to make impulsive purchasing decisions in the evening or at night.

Most people tend to be more charismatic — and more likely to inspire and motivate other people — earlier in the day, when they’re less tired.

So, what should you do?

Restructure Your Workday

Granted, it’s impossible to totally control your day. Things come up. Stuff happens.

But every job can be shaped, at least to some degree. Take mine. I get up early, so by noon or 1 p.m. I’m running low on mental energy. (To paraphrase South Park, blame glutamate.) Sure, I could keep grinding away, but the results usually aren’t great.

So, I intentionally switch to less mentally demanding tasks. Organizing. Answering emails. Doing simpler tasks that don’t require much in the way of focus and concentration. Or I’ll spend a few hours on a construction project, shifting the energy balance from mental to physical.

And so can you.

Whenever possible, structure your day so you can tackle tasks requiring focus and concentration as early in your workday as possible. (That’s also the best way to get your day off to a great start.) Or right after lunch, when you’ve had the chance to physically and mentally recharge.

Do the same for important decisions. By late afternoon, you’re much more likely to choose lower-effort actions that involve shorter-term rewards. Decision fatigue may cause you to reject an employee’s suggestion simply because it seems like too much work, or cause you to fire a struggling employee just so you no longer have to deal with him.

Decision fatigue may cause you to take the safe way out, and disregard a path with significant long-term upside.

When faced with an important decision late in the day, take a step back and ask yourself an even more important question: Can I put this decision off until tomorrow morning?

In most cases, you can, and should: If the stakes are truly high, the time to make that decision is when you’re at your mental best.

Science says so.