Returning home exhausted in the evening, it's common to blame work for the fatigue. However, a significant part of this tiredness may stem from the countless small choices we make throughout the day. This phenomenon, known as decisional fatigue, draws on a limited mental energy reserve, which can become depleted by the sheer number of decisions we face. In late September 2026, Spanish psychiatrist Marian Rojas Estapé discussed this concept on the radio program COPE. She explained that a large portion of daily exhaustion comes not from the workload itself but from the number of decisions we must make. Each choice, even small ones like what to wear or which message to reply to, consumes mental energy. This energy is primarily managed by the prefrontal cortex, the part of the brain responsible for control, reasoning, and planning. Making decisions requires mental effort. The prefrontal cortex is activated during each deliberate decision, weighing options, suppressing impulses, and planning. However, this area operates with limited energy, which is gradually used up by the many micro-decisions we make daily. Rojas compares the brain to a phone battery, which drains as decisions accumulate. When this mental energy drops too low, the quality of decisions declines. A tired brain may make random choices, delay decisions, or opt for the easiest path. Rojas notes that this is when people may act out of character, such as getting angry over minor issues or making impulsive decisions. While this model has sparked debate, as some studies have difficulty replicating the effects seen in laboratories, many people share the experience of feeling less clear-headed as the day progresses. One of the most cited examples of this phenomenon comes from courtrooms. Researchers analyzed over a thousand conditional release decisions and found that judges are more likely to grant sentence reductions at the start of a session than after a break, when fatigue sets in. After a real break, including a meal, the rate of favorable decisions increases significantly. This shows that decision-making, which should be based solely on the case, can be influenced by the time of day. This principle also applies to everyday life. By the end of the day, people are more prone to impulsive purchases, ready-made meals, or watching a series episode without a conscious decision. These behaviors are not signs of weakness but rather indications of a brain that has run low on decision-making energy. The solution lies in reducing the number of unimportant choices. Establishing strict morning routines, such as preparing clothes the day before or eating the same breakfast, can help reduce mental load and free up energy for important decisions. Many leaders also adopt nearly identical wardrobes to avoid making decisions about what to wear. Timing is crucial as well. Rojas advises tackling difficult decisions early in the day when the prefrontal cortex is still fresh and avoiding making important choices at night, when the brain is more likely to act on impulse. A break, a meal, or a good night's sleep can partially recharge the brain’s decision-making capacity, allowing for more thoughtful choices the next day.