The human biological adaptability
The human body's biological quick (and slow) response and adjustments towards changes and stresses of the environment - is remarkable.
When you put on a watch, while you're not used to wearing one - it feels weird in the beginning. But after you've worn it for a while - it feels weird taking it off. Your body has adapted to the constant wearing of the watch.
Eyesight can adapt just as quickly. If you spend an immense amount of time staring at a TV/computer screen, your eyes will naturally (maybe fast, maybe slowly), adjust to seeing with the shorter sight you need there.
If you spend more time outside, watching things that are further away like mountains or whatever - your sight will adjust to more far-sighted.
And yeah, same goes for back- and neck posture.
The sound-spectrum can be somewhat compared. If you wear hearing-protections for a day or week, or were to (peculiar enough) sit in a completely silent room for some amount of time, the first sound you hear would sound rather sharper than usual. A personal example; sometimes when I lay in bed to sleep, I listen to music. With the time passing, I need to turn the volume down bit by bit, because the current volume sounds louder and slightly more uncomfortable. I have also experienced opposite occurances.
Changes and habits in the daily life can form and shape unwillingly and unnoticed - but can also be guided or changed in different directions when noticed (or even unknowingly, for that matter). Many unmentioned factors play a role, but now if I have peaked your curiosity, you can research further yourself.