PTSD101: I think know what you mean. A quick and simple one-time interaction is not so hard for me but I don't want it to go further. Like, if you see the same person at a shop every day then you're supposed to develop some kind of deeper interaction with them and acknowledge that you are connected to some degree because you see them every day or several times every week or whatever. This makes me much more uncomfortable than if I were to go into a shop where I know nobody and don't expect to return any time soon.

I love anonymity - it makes me feel comfortable. Repeated or extended interaction starts to shatter my wall of anonymity and it makes me uncomfortable. I think that's the opposite of how humans are supposed to be unfortunately... you should feel more comfortable with specific people over time, not less.