Christians, what part of Jeremiah 9:4-5 17:5 should I not take to heart?

Paul is an approved apostle. Peter and the rest of the apostles would have cast him out, if he were not. Yet I don't see why you bring him up when simply asking about the book of Jeremiah. If the Bible says to take something to heart, take it to heart. If you don't believe in what the Bible says, then why are you asking what you should take to heart, if you don't care?