what gets our attention…

Oscar (13) left a jar of peanut butter and a knife out.
I call him, and comment: « I’m tired of always telling you the same things! »

He believes I’m talking about something else, and asks:
« What? Did I drink straight out of the bottle? did I leave my backpack lying around? Didn’t I close the rollerblades’ drawer? »

And then, I realize that he did not drink straight out of  the bottle, he did not leave my backpack lying around, and that he did close the drawer…

Why do we only notice what goes wrong?