Actually you sort of forgot a few of the lines also in the game
Where Graham talks about how the darkness in his life made him stronger. As someone once said "A Candle burns brightest in darkness" or something along those lines.
I think it is alluding to King Graham defying the fate of his existance, defying being a pawn in these endless struggled through darkness and light... and chosing both.
Chosing the bad with the good. Which isn't even the choice. Darkness and Light are not good and evil. Hense why Rosella's nightmare is a world of perpetual boring light and Alexander's is a world of darkness he cannot escape, they are both the struggles at their core character. Deciding that even though their lives have been tough, that there has been genuin joy, genuin strength to be had, and that the journey is what sustained them all through it.
Afterall this game is called "The Silver Lining"
Edit addition: Mind you I am mostly projecting what I imagine the great twist ending is.