Matthew 22:29 "Jesus answered and said unto them, Ye do err, not knowing the scriptures, nor the power of God." (KJV)
In other words we don't understand because we do not know the scriptures, nor the power of God. If we knew what God's word says then we would have the knowledge we need to deal with the everyday things that come our way. We would know God's will and we would not have to worry like we do.