I first registered the fact that my daughter would one day leave me when she was still really a baby. Katie had never crawled. But by around eighteen months she could not only walk but could put on her own clothes—swimsuits included. This she did one wintery evening, emerging from her room in a pink, tutu-style one-piece she’d apparently found in her drawer. After shrugging a raincoat over it and tugging on rainboots, she marched purposefully to the door.“Where are you going?” I asked.“Beach,” she replied, and reached for the doorknob.My husband and I exchanged glances. It was a freezing February night. The nearest beach was two hours away by car. I didn’t know how she figured to get there on her own, but it was clear she wasn’t giving up easily.“We can’t go to the beach right now,” I said. “It’s night-time. And cold.”“BEACH,” she repeated, rattling the doorknob.“The beach is closed now,” my husband offered. “There’s no one there. And there’s snow on the sand.”“Beach! Beach! Beach!” Katie chanted, and proceeded to pound on the door itself. Soon she was hurling herself at it, red-faced and tearful, devastated by this failed attempt at self-determination. As I scooped her up I found myself teary-eyed too—and not just due to suppressed laughter. As I carried her to the bathroom (“We’ll make a beach here,” I told her) I also felt a shiver of prescience. Up to that point, Katie’s life had been almost indistinguishable from my own: we woke and slept together; came and left together. There was rarely a moment when we weren’t somehow connected, and I’d come to take that connection for granted.But watching her fight so hard to leave that night made me understand something I really hadn’t before: that one day, my daughter would don her swimsuit, put her hand on the doorknob, and open that big wooden door with ease. Hey, Mom! I’m going to the beach.And slam—just like that, she’d be gone.The image caught in my throat, achingly sweet but painful, too. It was a feeling I’d have often in the years to come: dropping an outgrown dress into the Donations pile. Passing the playground that–at some point when I wasn’t paying attention–we somehow stopped going to play in. Sending Katie to school alone, armed only with a cell phone and attitude (of which thankfully she still has a lot).I felt it again the other night as I put her to bed. Now twelve, she looked up at me a little sadly.“I wish,” she said, “I could be little again. Do you wish that, Mommy?”“Yes,” I said, hugging her. And then: “No.”“Well, which is it?” she laughed.I hesitated for a moment, thinking. “Both,” I told her finally. “It’s contradictory.”For that, I’ve come to realize, is what parenthood really is: a lifelong, life-affirming dance of oppositional moments: clinging and cleaving; rejoicing and grieving. Putting on your swimsuit, and leaving. Or maybe just banging on the door, secretly relieved that — this time, at least –it won’t open to let you out.