One tip i heard from good ol jordan peterson is to force yourself to start making eye contact with people when you notice yourself slipping. It worked very well for me in party and on the street settings because it's a relatively easy task but such a simple gesture really opens the door to further interaction much wider. I never realized how much i was scowling and avoiding eye contact until i saw someone else doing exactly what i did. It was a terrifying experience and research afterwards was how i found this tip. It's very much in the realm of "just try this thing" type advice but i find that's what works best for me. All of a sudden I'm about to cut the spiral at the start and better engage with that "starting things" part of social life. I'm by no means perfect but damn i wish I'd learned more strategies in college when I'd regularly embarrass myself running from interest.

I hope you find a strategy that works for you. I know how impossible it feels to get back in but making eye contact and forcing a smile is something pretty much anyone can do. People want to talk to someone looking and smiling and often times will start the interaction themselves, saving me all the hard work!