Recently, I learned of a clever proverb in Japanese culture:
息の臭きは主知らず
Japanese Proverbs: Wit and Wisdom, by David Galef
iki no kusaki wa nushi shirazu
This proverb, literally means that the owner doesn’t know the stench of their own breath. Obviously this is not meant to be literal, instead it is about people being unaware of their own bad habits.
Another way of explaining it is that the eye cannot see itself. The eye needs a mirror. In the same way, we need to see the world around us, in order to see ourselves.
Namu Amida Butsu
Gleanings in Buddha-Fields 