Jeremiah is one of the more well-known prophets of the Old Testament. Today, the book of Jeremiah is loved by many. During his time, however, Jeremiah was not liked. In fact, many people wanted Jeremiah dead. There is a reason why Jeremiah was not liked.
Jeremiah prophesied against the wickedness of the Israelites. However, his prophecies are full of affirmation that God will not abandon His people. Sometimes, Jeremiah made contrasts between two sides to make a point. That is what is happening here.
Jeremiah had just finished prophesying against those who trust in mankind instead of the LORD. Jeremiah made the point that it is not a good thing to trust in man when you don't have more faith in the LORD. Fallible man will let you down. However, Jeremiah also made the point that it is wise to trust in the LORD, even when you cannot trust in man. Infallible God will not let you down.
How can we apply this today? We can all agree to trust in the LORD at all times. We can take our problems to God when we would rather take them to another friend. We can choose to listen to God and His word over our friends and neighbors. We can trust that God will not let us down.