I have a daughter who is now five years old. Until recently, I would have certainly killed myself if she had died. Without hesitation, I would have run to the nearest bridge and jumped. Continuing without her, bearing the constant grief, would have been completely pointless.
I felt this way even after my twins, her siblings, were born. My feelings for them during their first 18 months or so were nothing compared to those for her. I knew that losing one of them would devastate me, but at least I would still have had my oldest daughter, and that's what really mattered deep down.
It's only recently, in the past six months or so, that I feel it would somehow be possible to live on even if something happened to my eldest. The reason for this is certainly that I finally love the little ones just as much as her.
I don't know if the author had other children besides the daughter he lost. If not, then I wonder where he found the strength or even reason to move on.