system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do we get accustomed to things like glasses, rings, wrist watches etc on our body. Why do we not feel weird after some time as we do when we first wear them?

I've always felt that the glasses, jewelery etc are a part of my body. Its only when I touch them or see them that I feel there is something on my body which can be detached.
gpt
The human mind is conditioned to react to change because that skill is an important thing for basic survival. That tree sitting there, completely still, is not a threat. But the wild boar charging you from underneath it is. That rabbit that just moved could be a food source. And that spider crawling on your shoulder that you feel rather than see is possibly a threat too.

So these 'changes' in sensation are things your brain reacts to, and it filters out older stuff that get in the way of your ability to pay attention to those changes because you can only pay attention to so many things. 

A bracelet, a ring, a watch, even a dental filling feels weird at first. It's a change and it's out of place. But eventually your brain turns it off because other things are potentially more threatening or interesting for it to pay attention to.