The deep, personal material of the latter half of your life is your children. You can write about your parents when they're gone, but your children are still going to be here, and you're going to want them to come and visit you in the nursing home.
The whole conviction of my life now rests upon the belief that loneliness, far from being a rare and curious phenomenon, peculiar to myself and to a few other solitary men, is the central and inevitable fact of human existence.