"My dear friends, there are no friends," said Aristotle. It is self-delusion to expect that any relationship or friendship will last a lifetime. All connections dissolve in a cosmic ocean of time and space. At birth, family is closest. Friends in school and college are close. Later, fondness for colleagues, love for wife and children, and social connections appear to bind us. A time comes when such unions terminate physically and mentally.
The body and mind we love and nurture with food, fun, comforts and attachments also give prior warnings of abandonment by natural ageing or illness with no recourse. Nature has laws. One of them is what must meet, must separate too. "Separation" gets initiated the moment "meeting" commences. All associations and disassociations are predetermined plots beyond human understanding.
Had it been otherwise, we would have never switched off these connections. Soul encaged in body-mind combo is disinterested in temporal phenomena. Hence loneliness and a feeling of emptiness troubles in introspection. Our body, mind and soul go their own way into nothingness. How utterly helpless we are!
If this be the immutable law, then are we to remain aloof from all those who surround us? Answer: no. We need to "act" as co-passengers in a train, yet be prepared for separation without remorse when passengers board and deboard at different stations. Some leave us, and for some we shall leave. That is the journey of the life in loneliness, which appears terribly crowded. Why so? There's no answer to this.