This.

I was going to write words about all of the feelings, but this passage says it perfectly:

A first child is your own best foot forward, and how you do cheer those little feet as they strike out. You examine every turn of flesh for precocity, and crow it to the world. But the last one: the baby who trails her scent like a flag of surrender through your life when there will be no more coming after–oh, that’ s love by a different name. She’s the babe you hold in your arms for an hour after she’s gone to sleep. If you put her down in the crib, she might wake up changed and fly away. So instead you rock by the window, drinking the light from her skin, breathing her exhaled dreams. Your heart bays to the double crescent moons of closed lashes on her cheeks. She’s the one you can’t put down.

-Barbara Kingsolver, The Poisonwood Bible