I have social anxiety in very particular situations, usually things like approaching people to ask for help or similar, things where there is a significant chance of failure. This applies to the usual stuff like asking people on dates and extends as far as trying to use a coupon or asking questions about certain offers/services of cashiers, or even suggesting a place to eat when out with friends (I can manage that, but I have to frame it as a joke). It does not however apply to things that happen to me like if somebody dropped a bucket of paint on me or I slipped and fell over. It also does not apply to things where I feel I'm in a defensive position, like if somebody punched me and ran off I'd have no problem shouting them down in the middle of a busy street.
This is a bit weird I think, but still fairly usual social anxiety.
The problem is that the typically suggested remedy for this is more exposure. Force yourself to be in social situations that put you outside of your comfort zone and you'll eventually adapt to it. This makes sense to me (and it works with other things I'm afraid of) but it does not work with this. For me, a successful social interaction has very little or no effect. I feel no more able to do it the next time and there does not appear to be any improvement in my confidence. There could be a slight improvement but it doesn't seem to have done much over 10+ years I've been aware of this problem.
A bad social interaction however, has a very strong effect. I am constantly assaulted by unwanted memories of past social failures/embarrassments that never fade even when relaxing away from other people. They still feel extremely unpleasant and embarrassing, even going as far back as ten years ago. At the time of occurrence, they're even worse. A typical example was when I walked into a restaurant before its opening hours and tried to ask the staff for a table at the same time as they were trying to tell me to get out. I had been to this restaurant many times before and all of my experiences had been positive. Despite that, afterwards I spent an hour or more wandering the streets aimlessly, completely drained of all energy and will to do anything, experiencing a pain so strong it bordered on being actually physical.
So while positive experiences might be slowly pushing me forward, negative ones are definitely sending me back and I fear that increased exposure will actually lessen my ability to function in every day life. What do I do about this?