Decision Fatigue in Trading: What Happens to Your Brain After 3pm
Why traders make worse decisions later in the day — and how to protect your mental edge when it matters most.
I went down a bit of a rabbit hole… decision making.
And I found this super interesting study…
In 2011, researchers looked at how judges made parole decisions throughout the day.
Now you’d think the verdict would depend on the severity of the crime, the time served, the inmate’s behaviour…(basically is this guy a total scumbag, and does he deserve to be free?)
But one variable had the biggest impact was none of that…
It was the time of day.
Yep, weirdly, prisoners seen first thing in the morning were far more likely to be granted parole than those seen in the afternoon…. even when the cases were nearly identical!
Why?
Decision fatigue.
After a morning full of complex calls, the judges’ brains were simply tired.
So instead of weighing each case properly, they defaulted to the easier option: saying “no.”
(I guess it’s an easier decision to keep a dude locked up than risk releasing the wrong one…) 
And that brings us to trading…
DECISION FATIGUE
If you’re a day trader staring at charts for hours, watching price, taking trades, managing risk…
By the end of the session, your brain is going to be f*cked.
Just like the judges, you start defaulting to the easy (but wrong) decisions.
You miss good trades because you’re not on point and prepared You default to bad habits that are ‘easy’ for a tired brain You close early because that eliminates the anxiety of losing the unrealised P&L You chase crap setups just to stay engaged
Even if you trade US markets from Europe, burning mental energy in the morning on non-trading decisions (emails, errands, meetings) eats away at your limited reserves.
So what’s the answer?
The perfect answer is: make fewer decisions.
But we both know that life doesn’t work like that.
The realistic answer?
Be hyper-aware of decision fatigue Pace yourself… especially late in the session Walk away from the screen. Reset. Come back with resources spare. Use alerts and alarms. Save brainpower for the moments that matter. Do your thinking before the session starts. No unnecessary cognitive load during the trading day
“The mind must be given rest — it will rise improved and sharper after a good break.” – Seneca
And I get it… we all like to think we’re built different.
Maybe you are.
But in trading, one bad decision can ruin your week.
It doesn’t take many to wreck your month.
This game rewards good decisions… not time spent watching five-minute candles grind sideways.
Protect your mental edge like your dream depends on it… because it does.
Here’s the video that breaks down the judge study and the science behind decision fatigue. Worth a watch: