I feel like the way you observe the situation helps a lot. I tried to view everyone as "someone I already know" but I still get approach anxiety or even anxiety in general. Someone just told me this though and it really struck with me.

In like 80% of situations, people won't remember what you did or what you look like in the next minute UNLESS they felt embarrassed and were fearing you judging them. The only exceptions are at work/home/classes where the person sees you again and again and it's a build-up of their view of you. Even then, if you change over time and resist them putting you in a box, it's possible to erase their memory of those past situations for the most part. It's fucked because I don't remember how anyone I've been on the elevator with looks like. Even if they were weird. I don't remember the dude who was weird or awkward on the road. Even if I somehow remember the action I don't remember exactly how they look. And EVEN if I remember how they look AND what they did in an extreme case scenario, it doesn't affect how I'd act towards them because it's just electrical signals inside my brain. If someone is fading out in a group, I don't notice they're fading out. It's how they react to fading out that makes or breaks my respect for them. I just think instead that my friend and I are maybe ignoring our friend too much while he's chilling doing his own thing. It's like he can manage his own needs without or constant validation. They can be quiet and walking in the back and still come off as more grounded and confident even if they're not wanting to talk or can't relate. If he can't relate as much in the group, he's still able to be good friends with us on an individual level. Usually from my experience, the person has to be really charismatic when they speak or good looking to manage this though.