In order to believe that God will provide for us in our earthly needs we first have to be convinced that he has provided everything for us in spiritual lives, in relationship with Him.  Once we are convinced of the foundation that He really has done it all for us spiritually, we can begin to believe He can be trusted to meet our physical, emotional, mental and social needs as well. You can not jump ahead to try to apply Christ's teaching without first understanding His accomplishment through the resurrection.