My son is leaving for college, and it's the best and worst thing all at once.

I find myself struggling under the weight of change. My heart is simultaneously so full and yet shattered into a thousand pieces.

I am teary all the time. There's a heaviness on my shoulders that I'm not sure will ever go away.

My baby is about to leave the nest.

My high schooler.

Sure, I know what they say. I know this is an exciting time. I know he's better off launching into the world and growing into a responsible adult.

I know I will adapt to him being gone. I know he's not dying. I am extremely proud of what he's become and what he’s going to be. I know he's healthy, competent, and strong. I know that I don't want him living in my basement until he's 40. I know how lucky I am. I know this.

But I cannot seem make my heart understand what my mind knows.

All the many sleepless nights rocking a newborn in the moonlight of a tiny apartment, I dreamed of what he'd become.

Bleary-eyed and exhausted, I soaked it up as best I could. Later, as I wiped peanut butter off sticky fingers after his lunch every day, I fervently longed for when he'd learn to do it himself.

With each tantrum and missed nap, I'd ache for just a few minutes of alone time. When I had a baby girl in the shopping cart and felt frazzled as I struggled to herd two wandering little boys, I groaned and fantasized about doing the shopping without them.

A lot of those days, I found myself wishing for time to move faster. Life with young children was a never-ending glance at the clock on the wall, minutes sometimes ticking by so slowly they felt like hours. If I could just make it until nap time. Or bedtime. Or Friday evening at last.

Watching a child grow up can go by quickly. Image from iStock.

The dirty trick no one tells you is that one day, you will spend every minute wishing for the opposite: watching the clock and willing it to stop.

They never tell you that your heart will hurt and swell at the thought of time moving forward. And move forward it will, at a pace so rapid your head will spin.

You will wish and pray for just a few more months or hours or minutes with these babies. Few people ever warn you that you'll look back and wonder if you appreciated it enough, loved them enough, taught them enough.

I have worked for 18 long years for these exact results, and yet I feel unrealistically angry at my own success.

I have achieved the perfectly predictable end to the story I have spent years writing. I have worked myself out of the job. I knew this was the outcome of the path I was on, but now that I'm here, I want a different one. One where I get to have my cake and eat it, too. One where my son flourishes and grows, yet never leaves my side.

Is that too much to ask of the universe?

And if I can't have that, then I at least want a do-over.

My young man.

I want to hold him one more time in the moonlight of that crappy apartment, smell his sweetness, and lose an entire day with him in my arms.

Watching your children leave the nest can be exciting and scary. Image from iStock.

I want to see those sticky fingers grasp at Cheerios on a tray and rejoice when he can finally pinch one between them and raise it triumphantly to his lips. I want to see that toothless kindergarten grin look for me in the crowd of parents during the painful squeaks of the beginner violin concert and watch his eyes light up when he finds me. I want it so badly that every cell in my body just aches.

But that's the thing about this story: We don't get a different ending.

We get this one. We build our lives around these busy, toddling, energetic, lovable creatures, and they walk right out of it. We are left with a hole in our heart where their daily presence used to be — an ache that will never be filled because the life we had built with them in it is forever changed.

Stevie Nicks brilliantly said it best:

"And can I sail through the changing ocean tides / Can I handle the seasons of my life? / Oh oh I don't know, oh I don't know / Well, I've been afraid of changing / 'Cause I've built my life around you / But time makes you bolder / Even children get older / And I'm getting older too."

I know I'll be OK and find myself eventually on the other side of this long, lonely bridge.

I know it's not the end.

But it's the end of something; it's the end of something pretty spectacular. And I just can't help but wish it wasn't so.