What does it mean to be accustomed to seeing ourselves with this inversion?

It means you're used to looking at things like they’re upside down, even though they aren’t.

Imagine you wear a special pair of glasses that flip everything you see, like when you look at your favorite toy, it looks like it's standing on its head. At first, it feels strange and funny. But after a while, you get used to it. You don’t notice the flipping anymore because your brain has learned to adjust.

Like this:

You're used to seeing yourself with this inversion, just like you’re used to wearing those glasses all the time, even though everything is flipped, you still know what things are.

Imagine you're looking at a picture of yourself in a mirror. That's one kind of inversion, your left and right sides are swapped. It feels strange at first, but after a while, it becomes normal to you. You're used to seeing yourself like that.

So being accustomed to seeing ourselves with this inversion is just like being used to looking at things in the mirror or wearing those flipping glasses, it's normal now, even though it might seem strange to someone who hasn't seen it before.