Most people try very hard, incredibly hard, to hide that they are lonely or don't have friends. Most people would rather admit they're depressed and get some quick pills rather than say "I'm lonely." Saying you're lonely broadcasts that you feel insufficient and unsafe. Because of that, it's much harder to ask for help and therapy, or even admit and accept that you're socially isolated.

I don't think this is a "forever" state as you put it, but I think this is why some people suffer for so long (some researchers call this chronic loneliness [0]), and turn to fantasizing friendships as a way to cope.

I want to believe there's a way out, I'm not certain, but I think therapy and mindfulness could help, and also being around secure/empathetic people. Loneliness is kicked around as the bastard child of psychology and most practitioners will disregard a lonely person as simply depressed.

But taken to an extreme, according to attachment theory, there is a class of people who naturally gravitate to social isolation yet, paradoxically, desire closeness -- they're called avoidant personality types [1]. There is early research (Bowlby, Ainsworth, lots to read online) that trace the development of this behavior to experiences as an infant. I think these types of people could get stuck in their ways through their 30s and 40s.

[0] http://magazine.uchicago.edu/1012/features/the-nature-of-lon...

[1] https://www.reddit.com/r/AvPD/