If I close my eyes, I can conjure the feather-light weight of my newborn daughter. At under five pounds, my tiny bundle of love looked up at me with eyes so big and bright I swore they could discern my soul. No one warned me then of the chaotic parenthood journey ahead.

So many firsts and lasts would pepper our paths. Her first word, steps, and school day flew by amongst a whirlwind of activities designed to keep us both occupied—park play dates, music classes, and mom and baby yoga occupied much of our early days. I recorded everything in a journal, determined not to miss a moment let alone a milestone.

Her first tooth broke through when she was a few weeks shy of six months, she ate her first Cheerio seven weeks later, and she said “Mama” for the first time at 11 months. She repeated it three days later, and in some form or other (Mommy, Mom, Ma) every day since.

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As time went on and I became a busy parent of two, the journal fell to the wayside, and I have only just realized that I never thought to record the lasts. No matter how hard I try to jog my memory, I can’t recall the last time I brushed her hair, held her hand to cross the road, or picked her up. Had I known it would be the final time I would carry my daughter, I would have held on a little longer.

Now here we are, standing outside a 22-story residence hall at her new college, a place she worked so hard to reach. To say I am proud is a grave understatement. My daughter had more than enough obstacles put in her way, and she overcame them all with a level of grace and strength that awes me. She has more resilience and grit than any teen I’ve encountered and a kind enough heart to see the best in everyone. If anyone can do college, it’s this kid!

So why does my heart ache so much at the thought of the miles between us? (It’s 115, by the way.) It’s not because I think she won’t do well. I have no doubt she will. Yes, she’ll have her share of ups and downs, but that’s par for the course when you’re learning to “adult” at college.

Yes, I’m going to worry, I’m a mother after all. Will she find friends? Is she safe? Is she happy? Is she healthy? Will she eat any vegetables? These are thoughts that plague me daily, but they aren’t the cause of the pain in my chest. That, I’ve discovered, is a form of grief I only recently met. It’s a phase they never alerted me to when placing my new baby gently in my arms on her first day in the world.

As a friend said after dropping her eldest at college, “I feel as if I’ve left something important behind.” In my case, that something is a big chunk of my heart—no wonder it hurts. My energetic, funny, sweet, song-singing, cheesy-movie-watching daughter is all grown up, and she’s on a path that for the first time leads away from, instead of toward, me. I have to get used to not being the center of her universe while she (and her brother) will remain at the core of mine.

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So many have tried to reason with me, saying things like, “You need to put this in perspective; she’s not moving to Antarctica. She’s not going to war.” Some, sizing me up with judgment question, “Aren’t you happy for her?” Of course, I’m happy. My daughter is on an incredible path to becoming an even more amazing person. She’s preparing to make her proverbial mark on the world, and I can promise you it’s going to be an unforgettable one. I can’t wait to see the amazing things she accomplishes and hear about the people she has touched with her great wit, inspired ideas, and vast empathy.

As happy as I am for my daughter, I can’t deny myself that bit of sadness that accompanies any great change. While I’m excited to be a bystander on her journey, I find myself missing the many years that passed without me noticing. Where did that little toddler disappear to? The one who wore a Nemo swimsuit over Disney princess pajama pants? What about the braces-clad tween who danced around the living room? And the 16-year-old beauty who wrote the most touching song for me on Mother’s Day? I, too, feel as if I’ve left something very important behind.

At 18 years and 12 days of age, my daughter walked away from me toward her dorm, her outline blurred by my tears that refused to stop flowing. That was her last first day of college and my first day of learning to let go of the joy-giving bundle that once fit perfectly in the crook of my arm.