Been there. Done that. Blacked out. Forgot who I was, what I was thinking about, and how to distinguish one object from another in my field of vision. Lost touch with reality for a few seconds. Adjusted back and realized what the fuck just happened.

Yeah, it's a complete mindfuck (especially with a gravity bong) but I only do those hits occasionally because like you I have injured myself before, and even more often than that I've knocked over the bong in my stupor. Plus all that oxygen deprivation can't be good for your brain, but then again regular swimmers don't suffer from too many problems with that even though they hold their breath a lot.