In C.S. Lewis's "Mere Christianity," he explores the concept of what it means to be a Christian. He emphasizes that being a Christian does not imply being perfect or free from mistakes. Instead, it means having the strength to acknowledge failures, repent, and start anew. This process of renewal is facilitated by the presence of Christ within, which provides ongoing support and encouragement.

Lewis draws a parallel between the Christian experience and the voluntary sacrifice of Christ. Just as Christ faced challenges and ultimately died for humanity, Christians are enabled, through their faith, to face their own struggles and exhibit a form of self-denial and commitment. This internal transformation is essential for living a life that reflects the values of Christ.