Putting it bluntly, when I'm alone my world crumbles. I experience dark thoughts and sadness that is common in the ENFJ personality type. I will create a completely unrealistic world where I over think past interactions and realize where I've failed. I get stuck on what the other person thinks and feels (because it can never be good of course). I feel that I'm happiest when the people that I care about are happy, and in my mind when I'm alone those people are never happy and it is usually my fault. I get upset and sad, but I feel that I cannot express this to the people that I love because I do not want to appear weak to them. With that being said I'm pretty much trapped inside myself with eternal grief that makes me feel even more alone. I get to the point where I don't care about everyday life because it is almost unbearable. I think that this happens because I am unable to read how people feel when I am not with them, so my mind goes directly south...
OMG this has been me my entire life!!
Oh, the solution... I should have one, while I kinda am over this stuff. Realize that you are wrong when it comes to always thinking the worst is true. What helped me was also accepting to make mistakes; everyone makes mistakes! So also accept you can't be perfect in social settings, while nobody is. Just be you, and that's great.
Your friends (and family?) should like you, think you are awesome, or else you got the wrong friends. When you realize, hey, they do like me very much, and really really tell yourself this to be true, then hey, what gives if I'm not always perfect? That's being human.
And maybe meditation/yoga helps too. Eat healthy maybe as well, is wise anyway, and good sleep.