Have you ever thought of how, sometimes you see something so often that you cease to see it anymore? You look at it over and over and over again, for so many weeks or months or years that you forget what it actually looks like.. It may be years later that you suddenly realize something like 'Oh wow, this bedspread is such a pretty shade of green'.
It could be anything that you stop noticing... maybe a picture, maybe the sticky note on your desktop, maybe the wall clock in your bedroom.. and maybe, just maybe... even people.