well, the video explains it, that's because when you isolate yourself, you start expecting the worst from everyone else, you know, that kind of thoughts of "maybe they don't like me, are they laughing at me or with me?, they would be better without me" and that stuff.
is a Roundabout of negativity of "i feel vulnerable when i'm with people so i stay away from them and for that, i feel even more vulnerable. What i recommend you is, and i know it sounds like the typical advice someone who doesn't understand the affair would tell, to be more positive. They are not laughing at you and if they do, is not because they don't like you, maybe you just made something embarrassing, funny, but nothing bad.
and if i'm telling you is because that's what happens to me, is hard to try to avoid those thoughts that comes automatically, but is a good way to start.
what makes you feels bad about yourself is not to be in social situations, is that you cut yourself from social situations, is like when you take a too long nap on the day and when you wake up you feel tired and wanna go back to sleep, you feel safer alone so you want to go back and be alone, but that's not healthy, social interaction is a human need, like eating or sleeping, and denying it makes you sick.
Maybe you like to be by yourself, that's completely ok, but being totally alone and isolated hurts and kills you slowly, even if it's something you has looked for yourself