Not this again. PLEASE not this again.
Look I get it. As a society we do NOT want to stigmatize mental illness with the "pick yourself up by the bootstraps" mentality, because that's damaging to the struggle of the mentally ill (and social anxiety is a very real mental illness).
Except here's a secret: it works in a lot of cases.
I would know. I had THE WORST case of social anxiety as a teenager and young adult. I guarantee you. It was so bad that I went through middle school/most of high school without a single friend, only beginning to come out of my shell around my senior year. If you asked me a question between the ages of 14-16, my heart would immediately catch in my throat, my face would flush, my temples would start pounding, and all I'd be capable of giving you as an answer was a nod or a shake of the head. Even for questions which were not yes/no. It was that bad. I was known as the quiet kid (an oddly effective bully deterrent btw, nobody wants to mess with the quiet ones). There were always one or two people who would try to break me out of my shell and be friendly with me. I feel really bad in retrospect because I failed to latch on to their advances. They were really just trying to help but god-damn did I just want to be left alone.
Around the end of my junior year of high school I decided I did not want to live the rest of my life like this. I wanted a girlfriend, mainly, but also friends and mostly I just wanted to be able to say that I actually lived my life. At this point I felt like I was squandering it. So I began to crawl forward through my anxiety step by baby step. Inserting myself into increasingly uncomfortable situations until I became inured to the anxiety those situations caused. I actually got to go to my prom. I went on a few dates before high school was over. My social ineptitude (I was way out of practice) caused those dates to be total disasters, but fuck it I was putting myself out there. Freshman year of college provided an opportunity to start over as a new person and I took full advantage of that. The social anxiety was still there under the surface but I wasn't letting it stop me from putting myself out there. I made friends. I began to have a social life. By 21 I was married. Then divorced. Then engaged again by 25. Had many good friendships. Went through a few experimental life phases. I've faced many situations that most people are scared shitless of (like magic mushrooms). All with social anxiety lurking just under the surface. I just push through it the entire way.
If you've got some fucking nerve "pull yourself up by the bootstraps" really does work. It just takes a certain willingness to keep at it no matter what and to not be daunted by failure, until eventually you've rewired your brain to being that much closer to a functional normal human being's.