First little crack in my heart

Like any baby, Little One sometimes cries when she's hungry, or wet or dirty, or when she really feels she's suffered an intolerable lack of attention. Usually, though, she just sort of grumbles to get her point across, unless no one heeds the grumble, in which case she resorts to The Howl. Pretty rarely, though, does she really let go and cry.
Well last night I asked for it. You see, My Mother in Law bought Little One this really fabulous, beautiful cradle so that she could sleep near us for awhile. Little One is a fan. As long as it's daytime. But she gets seriously offended when she finds herself in there at night.
Little One's preference for sleeping is to be tummy to tummy with one of her parents. The cradle, you see, does not radiate heat. It is not soft and smooshy as, unfortunately, her mother is. It does not pat her on the back and say "shh shh" when she startles awake at night. Worst of all, she is positively forced to sleep on her back in there, which is just too insulting.
So I see where she's coming from. But, for so many reasons, she can't just sleep on people's tummies forever. So last night I declared to J, "We're getting serious about this cradle thing tonight. It's time to be tough". And he got the John Wayne glint in his eye and nodded in co-determination.
So we did the bedtime thing and we put her in the cradle. Just as anticipated, as soon as I put my head on the pillow- The Howl. So I picked her up and rocked her, and put her back in the cradle. Repeat. Repeat. Many grumbles and a few Howls later, she is SUPER sleepy, and she falls fast asleep. John Wayne and I give each other a little mental high-five, and we pass out also.
But, minutes later, she suddenly startles awake, finds herself not in contact with any tummies, and instantly starts crying. Really, really, all out, the-world-is-ending crying. So I scoop her up. I bring her in close and hold her tight. She snuggles her little bitty face up under my chin, and like a switch was flipped, falls right back asleep. She even looks like she's smiling a little. And I think, "wow". I didn't feed her, sing to her, hit her with a tranquilizer dart. She just needed to know I was There.
The thing is, in what seems like seconds, that will be gone. She won't want to be held so close, won't cry for me at night. Soon, my presence wont be enough to soothe her when she's upset. Looking at her peaceful little face in the middle of the night, I felt acutely aware of all that, and of how fast time seems to be moving these days. This will be the hardest thing about being a parent, I think. Loving someone so much, knowing that someday they're supposed to leave you. That the the days she wants to sleep on my tummy are finite, and few.
So I gave her a kiss and snuggled her a while, and just soaked it up. I admit it was pretty tempting to just forget the cradle. But. My job as her Mom is to pick her up when she cries, to comfort her and show her I'll always be here. But it's also my job to teach her how to sleep alone. It's a dichotomy I think every parent struggles with; how to protect and nurture and at the same time help her learn how to be independent. And I guess it starts already, at the very beginning really.
So I gave her one more cuddle and a kiss and I settled her back down in her cradle. And this time, she stayed asleep. I was relieved to get to take a nap, and proud of her for finally sleeping on her own for so long. But I'd be lying if I said that when I put her down and Let Go, it didn't break my heart, just a little.