The sort of loneliness that impacts life negatively is probably more of a mental space than a physical one. While Mandela was isolated, he was not without cause or without allies even if he was physically separated from them.
If you're on a purposeful mission you can endure a lot of destitution. The loneliness that is making the news is more of a secular malaise. People without purpose, task, meaningful communities to be part of, and so on. They might not even be literally lonely in a physical sense.
"Tell someone", just stop smoking, leave the drugs, find a career... be happy! Unless you are in jail. Realy is it that easy?
I think getting to a point in life where you are alone and haven't maintained any meaningful relation is very hard. It is not easy to just speak to someone random but also not sure it helps, unless the relation develops.
"So if you feel lonely, unless you're in solitary, please at least TELL SOMEONE how you feel... if nothing else. Tell me, I'll listen."
It's really not that easy. You can feel lonely in the company of supportive people or you can feel not lonely while in solitary.
I'm not saying loneliness isn't real... all I'm saying is, it is a choice that needs to be recognized as such, even if we keep choosing it over and over and can do no other sometimes.
So if you feel lonely, unless you're in solitary, please at least TELL SOMEONE how you feel... if nothing else. Tell me, I'll listen.