Singing is one of the most archetypal human forms of expression whether these might have been vocalizations and yodels or more sophisticated improvisations and melodies along with words.
However in our modern culture, people, especially those living in big cities, scarcely use this means of expression.

Modern lifestyle (with any type of complex or "blocking" it causes in the first place, establishing it as a form of "proper behavior" ) also deprives the humans of this very important and inherent way of expressing emotions, mood relieving, balancing the psychism, etc.

And here I would like to add something... It cannot certainly be regarded as a genuine means of expression, this kind of "singing" (being promoted during the last few years through TV talent shows) that is urging the candidates to "express themselves", thus very often being publicly humiliated, on one hand aiming for the profit (from the TV channels' point of view) and on the other hand for the few minutes of "reputation", on behalf of the participant.
So shallow it is unfortunately, the importance given to the act of singing, on behalf of the cheap bearers and transmitters of modern human civilization.

Fearing that I might have slightly drifted away because of the little comment above, I would like to return, deepening a little more on the subject of the psyche of the modern humans.
I would add one more important factor that affects the formation of the personality and the psychological background of a man .
It is the most direct environment to which a human relates... and of course, this is the family, most of the times.

It is not my authority to extend to such an analysis of the sociological and psychological elements of modern life and human evolution, I just wanted to place some arguments about how significant the mood or psychism is for the singing process, whether it concerns the professional singer or the person that just wants to express himself/herself with authenticity and sincerity.

The psychism is inextricably connected to the singing process, in my opinion.

For example, when someone has what we call a "good spirit" and is confident, then the sound of his/her singing voice is calm and free.
His/her song has a freely flowing energy and the voice fills the space.
The listener subconsciously perceives this specific "quality", feels the "balance" of the performer (depending on what he/she wants to express and point out) and surrenders with pleasure in the listening experience .

On the contrary when the mental state of the singer is negative or when there is insecurity and lack of confidence, all these are reflected in the sound, which becomes dull. The song does not have the required energy and there is a feeling that the body is not responding to the process! The flow of the breath seems to "slack"... and along with it, the voice and the expressive power also slack.
The listener subconsciously realizes again that something is not working properly, but usually can not decode and interpret the cause of this distress.

The voice is inside the body . Thus, since any mental or psychological condition directly affects the body, it is clear that it also affects (to a greater or lesser extent) the singing voice .

I emphasize the phrase: "to a greater or lesser extent", because the human mind has the ability to recognize, understand and suspend these psychosomatic symptoms that affect the function and performance of the voice (from the technical and interpretative point of view) during the singing process.
Therefore the unceasing quest for mental balance on behalf of the singer, is of great importance!

The authentic and honest expression through singing is priceless. For that very reason this specific "contact" with such an experience is pleasurably overwhelming for the singer himself that will convey it but also for the listener that will receive it.