You can diagnose your illness to some extent just by checking your symptoms. Similarly, when we shed the light of Gods Word on ourselves, we can diagnose our own spiritual state to some degree. Lets say that we have no joy even though God tells us to rejoice always in 1 Thessalonians 5:16. Can we say that we are leading a proper Christian life before God? Theres nothing at all that makes us lose joy as long as we believe that God helps us in every circumstance and eternal blessings in Heaven are waiting for us. In other words, we can check if our Christian life is on the right track in God just by seeing whether or not there is joy in us.