There is a sense in which I have not appropriated His death for me until I die with Him.  He died my death to be at-one with me.  I am to die His death to be at-one with Him.  When these two come together there is at-one-ment.  Atonement is not a legal transaction based on Christ death; it is a relationship of at-one-ness with Christ that we enter.

“Or have you forgotten that when we were joined with Christ Jesus in baptism, we joined him in his death?  For we died and were buried with Christ by baptism. And just as Christ was raised from the dead by the glorious power of the Father, now we also may live new lives.” Romans 6:3-4 (NLT)