Ok, going to try to make a comparison here; I *think* I experienced something similar to what UM seems to feel:
Today I went on a bit of a shopping spree and went to a new department store I had not been to before.
Usually, I go to one of a couple of department stores Debenhams or Selfridges, I'm on first name terms with the sections I regularly visit.
As I said though, today I went to the newish John Lewis store (it was getting late and I had no time to get to Debenhams). As I walked into the cosmetics section, I started to feel a little uncomfortable. The section was *very* quiet and so I got more attention than usual, and the section was staffed by a higher than usual number of very young and very pretty assistants, very few older senior staff at all.
For the first time in a long time I started to feel almost unwelcome, like I didn't belong. I almost walked through the department and back to my car, but I really needed to get something.
Fortunately, I know my cosmetics and once I started chatting to one of the girls about what I wanted I began to relax and everything was fine; even ended up having a laugh with a couple of them and stayed there longer than I planned.
The thing is, I went there with no makeup on and fairly scruffy jeans and top (I had originally only planned on going for a car wash, and ended up in the city). It really brought it home to me that even now I can feel uncomfortable when I'm not well dressed and presented.
Had I left when I felt nervous, I doubt I would ever go back there and it would have hurt my confidence.