(Sort of "What isn't the answer, part 2) Later in Reason for God, Keller says
The Biblical view of things is resurrection - not a future that is just a consolation for the life we never had but a restoration of the life you always wanted. This means that every horrible thing that ever happened will not only be undone and repaired but will in some way make the eventual glory and joy even greater.
Just after the climax of the trilogy The Lord of the Rings, Sam Gamgee discovers that his friend Gandalf was not dead (as he thought) but alive. He cries, "I thought you were dead! But then I thought I was dead myself! Is everything sad going to come untrue?" The answer of Christianity to that question is - yes. Everything sad is going to come untrue and it will somehow be greater for having once been broken and lost.
Having children after having struggled is a microcosm of that truth. I occasionally look in wonder at my living children in a way that would not be possible had I not been convinced for so long that this joy would never be mine. Sometimes, not often enough, when things get frantic around here, it makes me smile to think that Chris and I have, perhaps, more children than we can handle. During the dark times, in my wildest dreams, I never would have imagined it. God has been openhanded with me.
Lift up your eyes and look around;
all your children gather and come to you.
As surely as I live,” declares the LORD,
“you will wear them all as ornaments;
you will put them on, like a bride.
19 “Though you were ruined and made desolate
and your land laid waste,
now you will be too small for your people,
and those who devoured you will be far away.
20 The children born during your bereavement
will yet say in your hearing,
‘This place is too small for us;
give us more space to live in.’
21 Then you will say in your heart,
‘Who bore me these?
I was bereaved and barren;
I was exiled and rejected.
Who brought these up?
I was left all alone,
but these—where have they come from?’”
This is from Gilead, one of my favorite books. This quote is in a letter from a dying father, who lost his first wife and newborn, to the young son he never expected to have.
I'd never have believed I'd see a wife of mine doting on a child of mine. It still amazes me every time I think of it. I'm writing this in part to tell you that if you ever wonder what you've done in your life, and everyone does wonder sooner or later, you have been God's grace to me, a miracle, something more than a miracle. You may not remember me very well at all, and it may seem to you to be no great thing to have been the good child of an old man in a shabby little town you will no doubt leave behind. If only I had the words to tell you.**This is my offical internet notice that I want someone to read this to my children at my funeral.