It's simple, the concept of what love is, hammered into the brain from childhood by education, books, and movies, does not match the concept of real love that we experience during our lives - hence the disappointment.

Love is a feeling characteristic of a person, a deep attachment to another person or object, a feeling of deep sympathy. Love can reach a kind of perfect completeness of vital reciprocity and because of this become the highest symbol of ideal relations, an interpersonal beginning and a social whole.

But it happens when the fullness of life reciprocity is lost, ideal relationships are broken, and deep attachment to another person does not give the desired mental balance, then various mental disorders occur.

The World Health Organization (WHO) attributed love to mental illness by assigning it the number F63.9 (it is assigned to all scientifically recognized diseases). Moreover, they attributed love to mental disorders, to the item "Disorder of habits and urges", after alcoholism, gambling, drug addiction, kleptomania.

WHO has identified the following symptoms:

Obsessive thoughts about another person;
An inflated sense of self-worth;
Sudden mood swings;
Reckless, impulsive actions;
Self-pity;
Insomnia, intermittent sleep;
Changes in blood pressure;
Headaches;
Allergic reactions;
Obsession syndrome.
Researchers from the Faculty of Medicine of the National Autonomous University of Mexico, who share the point of view of the WHO, generally believe that love can last no more than 4 years, explaining this for physiological reasons.

A number of scientists believe that love can be compared to obsessive-compulsive disorder. In relation to love, another medical concept is also used - "altered state of consciousness", which mainly psychiatrists have to work with. In their opinion, consciousness can change both for the better and for the worse.