A Voice from the Past - Gregory of Nazianzen

Well, I have taken my stand, and looked forth; and behold a man riding on the clouds and he is very high, and his countenance is as the countenance of an Angel, and his vesture as the brightness of piercing lightning; and he lifts his hand toward the East, and cries with a loud voice. His voice is like the voice of a trumpet; and around about him is as it were a multitude of the Heavenly Host; and he saith, Today is salvation come unto the world, to that which is visible, and to that which is invisible. Christ is risen from the dead, rise ye with Him. Christ is returned again to Himself, return ye. Christ is freed from the tomb, be ye freed from the bond of sin. The gates of hell are opened, and death is destroyed, and the old Adam is put aside, and the New is fulfilled; if any man be in Christ he is a new creature; be ye renewed.

Gregory of Nazianzen, 330-390 AD, Oration XLV, The Second Oration on Easter, I (The Nicene and Post Nicene Fathers, Series 2, Volume VII, Philip Schaff and Henry Wace, translated by Charles Gordon Brown and James Edward Swallow, T & T Clark and Wm. B. Eerdmans Publishing, 1996, pp.422,423) 

How can we avoid taking for granted what Christ has done for us? What difference does it make?