Psychology of the masses and analysis of the human "I"

One of the most famous works of Sigmund Freud, written in the development of ideas expressed by Gustav Lebon in the book “The Psychology of Peoples and Masses”. The psychology of the crowd. How does it differ from the psychology of one particular individual? Why, being in the crowd, people often abandon their own “I” and let go of instincts that would never be allowed to manifest in ordinary circumstances? Where do fear, conscience and a sense of responsibility disappear? Why is the conscious perception of reality turn off in the crowd and individual features are erased?