The eyes believe themselves; the ears believe other people.

Related:

• What the people believe is true.
  Native American Proverb...
• The wise man has long ears and a short tongue. --
  German...
• The wise man has long ears and a short tongue.
  German...
• Choose a wife with your ears, not your eyes.
  French...
• An idea is not responsible for the people who believe
  in it...
• People will believe anything if you
  whisper it...