I've just come across this thread, and the first posters comments really resonated with me. I think for most people they experience these kinds of social anxieties as a teenager and learn to cope with them at that point. If they have a good teenage experience it creates abundance in their lives which seems to improve over time, if they have a bad experience as a teenager it spirals downwards and they become victims in life of the system by not having the self confidence to say what they want and need, people they interact with pick up on these weaknesses and use it to their advantages, and someone with a reflective personality, could pick up on this and shut down over time (potentially leading to depression).
On a day to day basis, i'm at a place in life where I'm pretty content, i now feel comfortable with saying what i want to/from people (but that doesn't necessarily mean i always get what i want). I have been confident, and have lost confidence, the loss has mainly stemmed from what others have said to me - "i appear unconfident / shy / quiet" - this is feedback that i have never asked for nor appreciate - but other people feel the need to say it. My advice to anyone who is in this situation - never listen to what others have to say - if you are content in life, who cares what others think. If you yourself feel you aren't content and want to up your game then that is you're choice. - I always look at the argument that actors and singers are very confident, but its fake, they use their confidence to make money - OUR society mostly see this as the norm, - it really isn't for most of us, most people don't have to act to make money, they have real skills.
I have highs and i have lows daily, and these balance pretty equally. However, i find that being on my own for long periods, (or even just an evening) the following day i will struggle to get out of bed and be able to socially interact. There is almost a void when I'm speaking to people the following day like i have lost the ability to make small talk or think of something to say. I would therefore never recommend anyone with social anxiety live or be on their own.
Over the last 5 years, where i work have really pushed my social interactions. They made all graduates in the company go on team building exercises. I hated every minute of it at the time - we had to share rooms, talk to people we didn't know, and generally try and grow as individuals. I was far behind the others in terms of my ability to do this, others seemed to make instant friends for life, whereas i was instantly guarded and didn't make any, i like my space, i prefer not to make small talk. Although i hated it at the time, not having my own space, i can remember that at the end, i felt more free to express an opinion or joke, something i would otherwise keep bottled up. I felt like i had been accepted into the group and that my opinion mattered. Im not sure what it is (but i can trace mine back to my teenage hood), but some people find this state of mind very easy, they feel comfortable to say what they want in others presence and aren't worried about consequences for their actions, for others it is really difficult.
So in summary, avoid living on your own, live with people who you can talk to and feel comfortable around - even if its your parents or siblings, not doing so will only hinder your feelings and ability to interact and potentially lead to depression or the feeling of loneliness. Try to find friends who respect you for who you are, faults included. Find ones who don't put you down, find ones who are like yourself and who can appreciate the ups and downs. If you are content, then don't let anyone tell you that you need to up your game, or tell you that who you are is wrong, this world has many different kinds of people - and not everyone is the same - we are however all contributors in some form.