Why our brain amplifies problems when we are mentally fatigued

What we really mean by cognitive fatigue

Cognitive fatigue is not simply a feeling of tiredness.
It refers to a state in which the mental resources required for attention, reasoning, and decision-making are temporarily reduced.

It commonly occurs when:

• large amounts of information must be processed over a sustained period,
• decisions are made continuously without adequate recovery time,
• one operates in demanding or uncertain environments,
• or when stress becomes chronic.

In this state, the brain continues to function, but it functions differently.

The central role of the prefrontal cortex

To understand what is happening, it is important to look at the prefrontal cortex.
This area, located at the front of the brain, plays a key role in:

• decision-making,
• planning,
• emotional regulation,
• prioritization,
• and the ability to step back and gain perspective.

It is this region that allows us to analyze situations calmly, to relativize, and to avoid reacting purely on an emotional basis.

Recent research conducted by the Paris Brain Institute has shown that during prolonged cognitive fatigue, certain substances involved in information transmission, such as glutamate*, can temporarily accumulate in the prefrontal cortex, reducing its efficiency.

In practical terms, this means that:

• reasoning becomes more effortful,
• the ability to gain distance decreases,
• emotional regulation becomes less stable.

The brain is not malfunctioning. It is simply no longer operating under optimal conditions for nuanced analysis.

* Glutamate is the brain’s main excitatory neurotransmitter. It plays a crucial role in information transmission between neurons. During prolonged mental effort, its local and temporary accumulation acts as a biological signal of saturation. This phenomenon is reversible and not pathological.

Why everything feels more serious or urgent

When the prefrontal cortex becomes less available, the brain relies more heavily on faster, more automatic and emotional circuits.

In this state:

• attention becomes less selective,
• negative or constraining signals take up more space,
• nuance is reduced,
• everything appears equally important.

A problem that would have felt manageable in a rested state may then be perceived as overwhelming or threatening. Cognitive psychology describes this clearly: fatigue reduces our ability to prioritize, creating the impression that difficulties are piling up.

The problems are not objectively more numerous. They simply occupy the same level of urgency in the mind.

Fatigue and altered decision-making

Cognitive fatigue also affects how decisions are made.

Research on decision fatigue, particularly the work of Roy Baumeister, shows that as mental resources decline, individuals tend to:

• postpone complex decisions,
• default to the easiest option,
• favor short-term solutions,
• or make more impulsive choices.

In these conditions, discomfort is often interpreted as a signal of urgency, when it is primarily a signal of cognitive saturation. Fatigue does not inherently produce poor judgment. It biases the evaluation of what is urgent, risky, or manageable.

How coaching can be beneficial in these situations?

In situations of cognitive fatigue, the primary challenge is not to find immediate solutions, but to restore mental conditions that allow for clear and accurate analysis.

This is where well-structured coaching can be beneficial.
Coaching provides a structured space in which to externalize thinking, reduce mental overload, re-establish priorities, and distinguish facts from perceptions amplified by fatigue.

From a cognitive perspective, verbalizing, structuring, and clarifying thoughts frees up attentional resources and supports a more stable form of reasoning. This framework makes it possible to revisit a situation with a rested mind, and with greater distance and discernment.

The coach’s role is not to decide on behalf of the individual, nor to provide ready-made solutions. It is to support a return to clarity, so that decisions are made in a more lucid state, rather than under the pressure of mental saturation.

For executives, managers, and highly engaged professionals, this work is particularly relevant. Fatigue does not erase skills or competence. It simply makes them temporarily less accessible.