I take it you won't be trying
this then?
If I stand facing railings like that I can deliberately make myself feel uneasy just by imagining the railings are not there, then switch it back off again by acknowledging that they are. I wonder if it would be possible to do it in reverse, imagining there are railings when there aren't.
I recall going to see a friend's boat once, the gang plank to it was about 15" wide, and up on stilts about 10 feet above the mud. I walked out onto it with no problem, then stood there chatting for several minutes, but after a while my interest in the conversation began to wander and I suddenly became
very preoccupied with the drop off the plank. That was it, the anxiety quickly became overpowering and there was no way I was getting it back under control, so I had to get off PDQ.