Human sensitivity manifests itself in the interplay of our instincts in the decisions we make. Human nature has been endowed with a sensitive apparatus that ensures the survival of both the individual and the species. We have a set of mechanisms—physical and emotional—oriented toward individual and collective survival: pain alerts us to danger; fear triggers responses to threats; hunger and sleep ensure bodily maintenance; and affection and empathy promote social cohesion and the continuity of life.

For example, we feel hunger, and this sensation is so crucial to an individual’s survival that its prolonged absence has serious consequences. Sustained loss of appetite can trigger malnutrition, weight loss, muscle weakness, deterioration of the immune system, and even negative effects on mood, concentration, and social life.

The same is true of a lack of sleep. When it becomes chronic, it profoundly affects physical, mental, and emotional health. It impairs concentration, memory, and cognitive performance and increases the risk of accidents. It also weakens the immune system, alters metabolism, and is associated with disease. On an emotional level, it increases irritability, anxiety, and the possibility of developing depression.

However, these mechanisms do not operate in humans as they do in animals. In the animal world, instinct is imperative; however, in humans, it presents itself with a weaker architecture. When faced with food, animals cannot avoid eating. Humans, on the other hand, even when hungry, can choose not to eat or to eat to a lesser extent.

This is evident, for example, in fasting practices. According to Harvard Medical School and the Mayo Clinic, intermittent or prolonged fasting—when carried out properly—can improve metabolism, reduce inflammation, and regulate insulin levels, promoting weight loss without compromising muscle mass. An article in the New England Journal of Medicine (Mattson et al., 2019) points out that fasting also improves cardiovascular health, increases insulin sensitivity, and protects the brain by activating processes such as autophagy and neurogenesis, which could have preventive effects against neurodegenerative diseases.

However, in the development of human personality—especially in young people—these sensitive mechanisms are typically not confronted, but rather followed without further reflection. Each of them presents itself accompanied by a pleasurable sensation, with the force of an immediate good, seeking to become imperative. After a good lunch, for example, sleepiness becomes the most attractive option.

But since these instincts are not strong in themselves, humans can choose to follow them or resist them in the name of higher criteria than sensible pleasure. Fulfilling a commitment or respecting another person are examples of greater goods that can guide our decisions beyond immediate impulse.

And it is important to note that every time a person chooses not to confront an instinct that opposes a higher good, this instinct is strengthened. Over time, it can acquire such strength that it ends up dominating the will, to the point where the person can no longer do anything but follow it. That is, they lose the ability to decide freely.

Therefore, in the maturation process of the human personality—and especially in the formative stage—it is essential to understand that these sensory mechanisms serve a function, but cannot be managed as ends in themselves. The greatest risk facing human beings is being driven solely by the pursuit of sensory pleasure, thus losing their capacity for self-control.