Before the Beginning

Today I was studying for a teaching I am doing called "Before the Beginning" (Genesis 1) and was tipped off to this quote by C.S Lewis about the love of the trinity before the beginning:
For in self-giving we touch a rhythm not only of creation but of all being. For the Eternal Word also gives Himself in sacrifice; and that not only on Calvary. For when He was crucified He ‘did that in the wild weather of His outlying provinces which He had done at home in glory and gladness’ from the foundation of the world… And as the Son glorifies the Father, the Father also glorifies the Son… From the highest to the lowest, self exists to be abdicated and, by that abdication, becomes more truly self, to be thereupon yet the more abdicated, and so forever. This is not a… law from which we can escape… What is outside the system of self-giving… is simply and solely Hell… that fierce imprisonment in the self… Self-giving is absolute reality. (The Problem of Pain, 157,158)
We could never be self-giving if the Lord Jesus has not intervened at the cross and brought us into the love of the Trinity. This is was Jesus' prayer:
John 17:5 And now, Father, glorify me in your own presence with the glory that I had with you before the world existed.
John 17:24 Father, I desire that they also, whom you have given me, may be with me where I am, to see my glory that you have given me because you loved me before the foundation of the world.