To the new parents next to Room 9:

I saw you when we were unloading our luggage today. I watched you walk your crying 6-month-old around the lawn, bouncing her gently as she fussed.

I said hello when you entered your room—you were trying to quietly open the door as to not wake the sleeping baby on your shoulder. You were weary. And a little overwhelmed. Parenthood looked so new on you.

I witnessed you switching off baby duty—one taking a rest while the other one soothed and fed and carried the baby. I heard you wake up early and walk your little one down to the sandy shores of the lake. I saw how you never really had a break and how she was always in your arms.

All week as my family was in and out of Room 9, I watched your family enter and exit the room right next to ours. And I thought to myself how strange it must be for you, to watch us, parents with two gangly teenagers who are both taller than their mom. Our babies are not much of babies anymore, they are more grown people with their own thoughts and attitudes and ideas of the world.

RELATED: The Stage That Sneaks Up on Mamas Raising Little Boys

Our babies can pack their own suitcases for vacation and unload the car. They can be left alone, unsupervised while their dad and I talk on the lawn under the stars. We don’t have to wake up early or go in for nap time or bounce them on our laps. We do still have to feed them every two hours, however, so I guess some things will never change.

There were so many words of wisdom I wanted to tell you, new parents next to Room 9. I wanted to tell you to hang in there, that it will get a tiny bit easier. I wanted to tell you that you are doing a good job. I wanted to let you know that this baby phase really won’t last forever even though when you’re in the middle of it it seems like it will.

But mainly I wanted to tell you that this parent thing is hard. It is not for the faint of heart. You will spend so many hours wondering if you are doing it right, questioning why there is not a class on “How To Raise Humans” you could enroll in somewhere. You will cry—a lot. But you will also laugh harder than you have ever laughed before. You will find there is a joy so deep that it is overflowing into your face and eyes and every corner of your soul.

I know it’s hard to believe now, but one day you will have teenagers who steal your heart by the jokes they tell or the way they reach out to help you. You will watch them grow into compassionate and good people and you will weep with the promise of who they are going to be.

And one day, you will be staying in a room on vacation and you will watch a young couple who have become new parents and your heart will have a funny ache in it. You will wonder what that funny ache is—that twinge of something, that catch in the back of your throat.

RELATED: 10 Things Girl Moms Have To Look Forward To About the Teenage Years (Really!)

You will look at your teenagers and stare into their eyes and realize that funny little ache is because you can still see their baby face when you look hard enough. Behind the shaggy hair and braces and headphones, you will see the chubby, squishy face that once laid on your shoulder. And you will remember that your whole world was once able to be held in your arms.

It will make you sad for a few minutes, but then your whole world bounces up to you and grabs your arm and drags you down to the lake. You splash in the water and skip stones and you will begin to understand that it’s time to let go.

You will be struck a thousand times over with how bittersweet it all is, and you will wish for just one more moment when you could smell their baby goodness and cradle them to your chest.

Then just as you are about to cry again with the impossible heartache of it all, one of them will throw sand at the other one. The sand thrower will laugh and the girl will sigh an impossibly long sigh and stomp off to the room. You will reprimand both of them and ask why they simply can’t enjoy each other and how long will it take for them to get along. In that moment, you will think to yourself that maybe them growing up isn’t such a bad thing after all.

I guess that’s what parenting is all about, New parents next to Room 9. It’s hard and sad and happy and exhausting and everything in between. And in the end, it’s all beautiful.