Parenting is rewarding, but it is also challenging. It is a full-time, rest-of-your life job.

You always think — hope — that whatever difficulty you are facing with one period of a child’s life and development will simply be solved when he or she grows out of that phase. Soon, they’ll be potty trained, or be able to retrieve their own snacks, or walk home from school alone, or whatever.

But, what one soon discovers is that one phase of difficulties is only replaced by the difficulties of the next. Parenting doesn’t necessarily get easier, it is simply transformed. There are new joys, but also new headaches.

And, I find that the headache part is the part parents feel tremendous shame disclosing. Our modern, parenting-book, social-media-sharing culture seems to dictate that the only thing that one can say about parenting is that “it is the most important and fulfilling thing I’ve ever done.” That is the only way that one is allowed to signify that one loves his or her children and has made the sufficient level of sacrifice.

I find those constraints ridiculous and impossible. It is possible to love your children complete and simultaneously be exhausted by them. For many parents, that is the truth, and there is nothing shameful about acknowledging that.

Since my oldest son was 6 and my twins were 3, I have been a single dad. Even though I have always had demanding jobs, I threw myself fully into my role as a father, making breakfast every morning and dinner every evening. (Sometimes a babysitter would do that, and I was thankful for the help.)

You do what is required of you as a parent. You rise to the challenge. You make it to every school activity, sporting event and music recital. You arrange the play dates, sleepovers and birthday parties. You make the 1 a.m. run through the snowstorm to get the fever-reducing medicine and you change the bedding and mop the floor when a stomach virus turns their room into a scene from “The Exorcist.”

You enjoy the good times, vacations and the family game nights or pizza-and-a-movie nights, but, at least for me, the years wear on and the fatigue of it all slowly begins to set in. It is easy to forget that you owe it to yourself to have a separate personal life, that you were a fully formed independent adult before them and you will have to be again when they are gone.

It wasn’t until the younger two were seniors in high school that it dawned on me that I had not been on an actual vacation in more than 10 years. Sure, I traveled — for work, with my daughter to her fencing tournaments, to professional conferences, to take the children to visit their grandparents — but, none of that was particularly relaxing or designed to be.

I believe that in my head, at least for the past four years my children were in high school and in my house, I had a countdown clock in my head: I just had to hold out and maintain them as my priority in life for a little while longer and then they would go away to college and my life would finally begin.

That day finally came four years ago when my twins went away to college. I was now officially an empty nester. I was 45 years old and I had only ever lived alone for four months in my life, and for those four months I was engaged to be married.

People often ask me if I was sad that the children had gone away, expecting me to say how lost and lonely I was. I didn’t. I told them how free I felt, how I felt that I was entering a new life of my own, and I felt absolutely no guilt about that.

I traveled. I reconnected with old friends and made new ones. And, I was able to work as long and as hard as I liked and never had to worry that there were children at home who needed me there.

But, now that the children have graduated and moved back into my house as they search for jobs and eventually first apartments, I will say the thing that we as parents are not supposed to say: What happened to my empty nest? The very definition of home has changed. Mine will always be their family home, their spiritual home, but it cannot be their primary home. This is now my primary home, alone.

I know that this arrangement is temporary, and I want to help my children out in every way possible, but it would be dishonest to say that their reappearance in “their rooms,” which I now call guest rooms, has been jarring.

No matter how much I try to resist the urge, I’m reverting to my last-phase parenting mode — worrying about whether they’re eating enough and eating healthfully, washing their clothes and taking them to their rooms.

These are young adults and not children. I have to remember that. I also have to remember that this phase is temporary. But, I also have to prevent them from dragging their feet leaving home and starting their own lives.

When your children return to your empty nest, it is a good thing to firmly nudge them out. That, too, is what love looks like.

Charles Blow is an Op-Ed columnist for The New York Times.