Hey there,
I've been in a pretty bad place myself for a number of years, but everyone's experience and perspective is unique, so I won't pretend to understand exactly what you're going through. What I would suggest is:
1) Try to maintain contact with the good people in your life. You know who they are if you really think about it. Some people are fair weather friends, others genuinely care. In some of the major rough patches of my life, I pushed away some very good people out of my life due to my own insecurities. I deeply regret that now, so try to avoid it if possible, even though I totally understand that when you feel really depressed, you kinda want to just disappear and be left alone.
2) Try to find at least one caring person to be fully honest about. I bottled up my problems for years, I am instinctively a very private individual, but when I shared my honest thoughts with a close friend, it felt like a weight lifted. He doesn't even need to fully understand. Just the act of sharing is a relief. (Make sure you do pick somebody patient and caring, and don't just use that individual as an ear to vent on. Be a friend to him/her too above all else. Nobody likes to just be constantly bombarded with misery.)
3) Consciously look for positive stories and positive people to be around. If you look for evidence of what's wrong in our world, you will find plenty, and it is soul crushingly depressing. But there is also much genuine beauty and hope too. This is a world where the Syrian government bombs its own children with barrel bombs and chemical weapons, and yet toppling the regime will likely lead to an even darker future for the people of Syria. At the same time, amazing people adopt special needs children from the other side of the world, despite the immense material cost and emotional challenge it presents, just to give a child a better life and a family. Our world is wondrously beautiful and horribly ugly all at the same time, as an individual, you can only choose what you want to see.
