Being "lonely" is a feeling that transcends the external environment and social activities. While someone can be surrounded by people in a crowd and still feel lonely, and someone else may be alone without anyone, and feel no loneliness at all, the feeling of loneliness is Disconnect the outside inside.
Feeling lonely is just a feeling, not a fact. When you feel alone, it is because something has awakened the memory of that feeling, not because you are actually isolated alone. The brain is determined to pay attention to pain and danger, including feelings of fear and psychological pain, so the sense of loneliness works to alert the brain, but then the brain tries to understand this feeling. Why do I feel this way? Is it because no one loves me? Because I failed? Or because people are bad? Then the brain begins to confuse emotions with facts. Then the problem increases, so you have to fully realize that what you are facing is just a feeling and you should accept it without overreacting