We tend to desire the things of this world more than we desire God or what God wants for us.  And we tend to be blind to the blessings that come from truly giving our lives over to him like Jesus commands us to in Matthew 16.  The problem is that by holding onto our life or the things in our life, we are trading the blessings of God for the false blessings of this world.  We need to let go and give our full lives to Jesus.