Do You Love Me?

After Jesus’ death and resurrection, Jesus asked this question of Peter three times.  Do you love me?  And each time, Peter just couldn’t respond in a way that matched Jesus’ expectation of sacrificial love.  Why is this?  I think it was because at this point, before he had been empowered by the Holy Spirit, Peter was still very much a carnal believer and not a mature disciple of Jesus Christ.