When somebody says to you the same thing over and over again about anything like: eat your food, eat your food, eat it !! blabla !! and someday you discover this person is sick because she/he was not eating properly. Then you could yell : TAKE YOUR OWN ADVICE !
or...
Sometimes we are perfectly aware of what is happening and we know which path we have to choose or what we should do, but we are weak, not strong enough to follow what we already have in our heads... we know the answer... we know that we know the answer and we refuse to follow our own advice, generally because of fear. ^^
"Advice is what we ask for when we already know the answer, but wish we didn't" --- Alice in Wonderland.