If our identity is a bit part in the world's play, then what we do may look OK for a while but the plot will fray as time goes on. It's the wrong script for the stage God made. Things get broken and we wonder why the life we have been dealt isn't fair, isn't what we expected. Life doesn't work because it is the wrong life for this world.
Contrary-wise, if your identity really is in Christ's story, then... life still won't work but for an entirely different reason. Your life as a Christian, "all such good works as Thou hast prepared for us to walk in", your part in the story, works for God's story but not in the world. The whole world is trying to make a different story, their individual stories, take place on the same stage. You, like John and Stephen and Mary and Lydia and Peter, gum up the works, finding yourself at odds with every non-Christian and their agendas.
The insufficiency of Christ for the world's story surfaces quickly because He is not interested in another play, a different plot line, someone else's story. This is why the disciples were so frustrated with Jesus. This is perhaps, as suggested in Jesus Christ Superstar, why Judas betrayed Jesus - trying to get Him to play His hand, trying to force a different story. We are all Judas's in that regard. We have been taught to "invite Jesus into our lives". Very wrong message. We must, rather, accept Jesus' invitation for us to join HIS life. Otherwise, He must, in order to remain true to His agenda, remain insufficient for ours.
Our identity has to be found as a player in His story. In order for Jesus to make any sense at all in our lives we really do have to die to ourselves and accept another, different, not our, view of who we are. We are chosen before the foundations of the world. We have a different name. We are God's handiwork with work to do for Him.
But everyone thinks they are someone else than God has intended them to be. Third Day's "In time will I be what You're thinking of? Rescue me." We must change who we think we are. Accept who God thinks we are...knows who we are.