What are the key moments that help push the father to keep striving in the book "The Road" by Cormac McCarthy

I think that the only thing that pushes the father is his love for his son. The moments between the father and his son are largely silent yet filled filled with an atmosphere of uncompromising unconditional love. When the two find the oasis-like underground bunker they share many tender moments. one of my favourite lines in the book kind of sums father's feelings for his son, "If he is not the word of God, God never spoke."

Thanks so much :)