Your young adult child is not just spending less time at home, but may be moving out permanently. While you grief over the "loss", the empty nest stage can be one of great personal growth and satisfaction.
Parenting doesn't cease even as we let go of our children; it simply takes a different form. Learn to be your young adult's best friend, parenting from afar instead of watching over them closely.
Husbands and wives whose marriages were centred around their children may suddenly find they have nothing in common anymore and struggle to relate to each other. But it's never too late to rekindle the intimacy and purpose of your marriage in its pre-parenting years.
Elderly parents may be taking up more of your time than your children. Make sure you live out your relationship with them in a way that leaves no regrets when they are gone.