Why Are You a Christian? (Ephesians 6:10-20; LD 12)

The weapons listed for our Christian armor are mostly defensive weapons.  If these are defensive weapons what are we defending ourselves from?  How hard can it be for us to go about this age if we are grounded in Christ?  If we are already called a Christian then why such a struggle? So, why are we called Christians that is anointed by Christ if we are just walking through this world?